Oct 11 2021

Reopening Schools Safely in California: District Examples of Multilayered Mitigation

At the same time that schools are reopening across the country, hospitals in many locations are buckling ­under a wave of new COVID-19 patients due to the spread of the highly contagious Delta variant of the virus. To keep students, school staff, and their families safe while continuing the vital work of educating students in person, it is imperative that schools implement evidence-­based, multilayered mitigation strategies that prevent in-­school transmission, including masking, vaccination, testing, contact tracing, quarantining, handwashing, and ventilation. When coupled with strong communication and attention to social and emotional needs, ­these mitigation strategies can help districts ensure that students can safely return to—­and remain in—­in-­person learning.

Over the past several weeks, schools across California have reopened for the 2021–22 school year and are engaged in the challenging but crucial work of ensuring students can safely participate in in-­person learning. The state has enacted several first-­in-­the-­nation public health policies to support safe school reopening, including a renewed mask mandate for schools, issued in July 2021; a requirement for all school staff to be vaccinated or undergo regular testing, issued in August; and a requirement for students in middle and high school grades to be vaccinated, once the vaccines receive full approval from the federal Food and Drug Administration. In addition, the state has offered resources to support ­free school-­based testing and vaccine clinics, and established rapid response teams to bring additional testing capacity to schools that experience outbreaks. With ­these public health policies in place, California’s COVID-19 case rate has steadily declined since mid-­August. As of September 20, 2021, the state had the lowest case rate in the nation, although some areas of the state—­primarily regions of the Central Valley and parts of rural Northern California—­continue to experience high case and hospitalization rates that are straining local hospitals.

Drawing from district documents and websites, as well as media coverage and our own interviews, this brief compiles preliminary information on reopening for the 2021–22 school year in several California districts that are using multilayered mitigation to keep schools open and students, staff, and their families safe.

How Are Districts Implementing COVID-19 Testing?

Though it can be a logistical challenge, regularly scheduled COVID-19 testing can greatly reduce or eliminate in-­school transmission of the virus. All of the districts have COVID-19 testing programs, with some districts, like Yuba City and Chula Vista, leveraging state resources to support their efforts. Chula Vista, Long Beach, and Los Angeles Unified School District (LAUSD) have also used widespread testing as a strategy for identifying positive cases and initiating proactive self-­isolation and quarantine protocols to minimize the risk of in-school transmission.

In Chula Vista, the district built upon its original February 2021 testing pi­lot, which served as a model for other districts. In a two-­week rotation that began on August 2, 2021, Chula Vista offers asymptomatic testing at each school for students and staff. Once parents opt in, students are automatically tested during the school day on a 2-­week cadence; walk-in testing is also available Monday through Friday at the district’s central office. For asymptomatic individuals, the district administers rapid antigen tests. If a student tests positive, the district administers a follow-up PCR test to confirm the result. Students who are symptomatic or test positive are required to submit proof of a negative PCR test result before returning to in-­person learning. As of September 8, 2021, up to 700 ­people per day ­were tested through the district’s partnership with Maxim Healthcare Staff ­Services, the fire department, and the state’s testing lab.

Both Long Beach and LAUSD have asymptomatic surveillance testing programs in place and leveraged this strategy to help identify positive cases prior to or at the beginning of the school year. In Long Beach, unvaccinated students ­were required to register for testing that occurred during the first 3 weeks of school. Tests ­were conducted using an anterior nasal swab. To help parents and caregivers register, the district created a cheat sheet, available in multiple languages, as well as a video explainer. In the first 3 weeks of school, Long Beach administered more than 60,000 tests, which showed an overall positivity rate of less than 1% and decreasing weekly positivity rates. On September 23, 2021, Long Beach announced that it would adopt a randomized testing strategy to allow for weekly testing of a representative student sample—10% of each school’s unvaccinated student population—­while also minimizing testing burden for students and schools. To minimize bias, the randomized list of students is generated each week using an automated system.

In LAUSD, the district requires weekly PCR testing for all students and staff and has been held up as a national model for testing and tracing. LAUSD has 12 stationary testing sites, and each school receives a weekly scheduled visit from mobile testing teams who conduct screening testing for all students and staff on campus. This work is funded by COVID-19 relief funds; the district is also pursuing reimbursement from the Federal Emergency Management Agency for costs associated with COVID-19 testing, tracing, and vaccinations. Contracted health care workers from three organ­izations staff ­these stationary testing sites and mobile testing teams. PCR tests are sent to SummerBio, an external lab, for pro­cessing. Individual test results are then posted in the district’s Daily Pass, a web-­based application, within 24–36 hours of test administration. In total, approximately 100,000 individuals per day are tested.

From August 16 through August 27, LAUSD administered over 1 million nasal swab PCR tests, which ­were supplemented with rapid antigen tests as needed. Rapid antigen testing is used in special circumstances, including to admit a student who may be temporarily out of compliance with the weekly PCR testing requirement. The district plans to continue weekly PCR testing for all students and staff, regardless of vaccination status, and reports active cases and case rates through school and district testing report cards. If students need to be tested for a specific reason (e.g., exposure), they can book a test and receive results and messages through the district’s Daily Pass.

To communicate with school and district community members about testing protocols and pro­cesses, LAUSD uses its Safe Steps to Safe Schools website, which has information about all COVID-19 safety protocols. Principals also receive bulletins informing them of any changes to protocols, as well as toolkits and resources for communicating about ­these protocols with families.

What Strategies Are Districts Using to Facilitate Contact Tracing, Including Implementation of Stable Groups?

All of the districts profiled in this brief are conducting contact tracing following exposure to suspected or confirmed positive cases. Several districts have designated school or district COVID-19 liaisons to assist the local health department with contact tracing, a practice recommended in state guidance. For example, Yuba City has identified three district office administrators who serve as COVID-19 liaisons and lead contact tracers. In addition, each school site has a COVID-19 liaison who assists with contact tracing. District staff serving as contact tracers have received training from the region’s Bi-County Public Health Department and are responsible for managing and supporting contact tracing, notifying exposed individuals, creating and maintaining a database of exposed students and staff, and communicating with the local public health department.

In LAUSD, approximately 27 district-­based staff members, including administrative aides and ­human resources representatives, work alongside approximately 400 contracted staff on LAUSD’s contact tracing team. When a student or staff member tests positive, a new case is created in the district’s tracking system. School principals, who serve as site-­level COVID-19 liaisons, assem­ble a list of likely close contacts for the infected individual and submit this list to the tracing team. Once the positive case is identified, the team reaches out to conduct a phone interview with the positive staff member or parents of the positive student. The school site administrator notifies suspected close contacts in person or via phone within 24 hours of suspected exposure. If the close contacts are still in school, they are sent home with quarantine instructions. In addition, any employee who has accessed the school via their Daily Pass receives an automated notification each time ­there is a positive case at their school. LAUSD representatives also meet twice weekly with investigators from the Los Angeles County Department of Health to review evidence of any potential in-­school transmission. School principals have access to school-­level dashboards in Daily Pass to monitor positive cases at their sites.

Organ­izing students into stable groups, or cohorts, can aid districts with contact tracing, as well as help prevent COVID-19 outbreaks by reducing the number of contacts each student has. In Cajon Valley, elementary students are cohorted by classroom; ­middle school students may be cohorted by grade level, depending upon the size of the school. To facilitate contact tracing, the district encourages schools to keep students together in their stable groups during mealtimes and on the playground; to seat students in groups of four or two, depending on ­table shape, when eating outside; and to use seating charts. The district also employs rotating schedules to minimize mixing among stable groups in common spaces.

How Are Districts Managing Quarantine, Including Addressing Staffing Challenges When Educators Must Quarantine?

Quarantining close contacts of infected individuals has been a necessary hallmark of COVID-19 mitigation, but instructional time can be ­limited when students or teachers must quarantine. In some districts that attempted to reopen in fall 2020, teacher quarantines led to severe staffing shortages and school closures. Since then, vaccines have become widely available, and science has established that masking is a ­simple yet highly effective strategy for preventing viral transmission. Based on the efficacy of vaccines and masks, California issued updated quarantine procedures for schools to use when individuals are vaccinated or masked at the time of exposure. This guidance has informed the quarantine policies of the districts profiled in this brief.

Fully vaccinated individuals can avoid quarantine following exposure to a person with known or suspected COVID-19 infection if they are asymptomatic. If unvaccinated at the time of exposure, school staff must follow standard quarantine procedure, which requires close contacts (defined as having spent more than 15 cumulative minutes over 24 hours within 6 feet of an infected individual within 2 days of symptom onset or positive test) to quarantine for 10 days from exposure without testing, or for 7 days if they have a negative test result on or ­after day 5. Unvaccinated students may follow a modified quarantine procedure that allows them to remain in school following an exposure if both parties ­were wearing a mask at the time of exposure and the close contact remains asymptomatic, continues to wear a mask, undergoes at least twice-­weekly testing during quarantine, and continues to quarantine for all extracurricular activities, including sports and activities in the community.

Since schools first closed in spring 2020, the San Diego County Office of Education has focused its efforts on providing technical assistance to support districts with school reopening. This has included close coordination and partnership with San Diego County’s Health and ­Human Ser­vices Agency and the development of tools that help districts implement state and federal guidance. To assist districts with communicating and implementing the state’s updated quarantine guidelines, the San Diego County Office of Education issued a quarantine decision tree that accounts for differing procedures for students and staff, and dif­fer­ent protocols based on an individual’s vaccination and masking status at the time of exposure (Figure 1). Cajon Valley and Chula Vista, both located in San Diego County, included this decision tree in their district reopening plans.

Source: San Diego County Office of Education. (2021). COVID-19 k–12 decision trees. https://covid-19.sdcoe.net/portals/covid-19/Documents/Health%20Practices/COVID-19-Decision-Tree.pdf (accessed 10/05/21).

To address staffing challenges that arise when teachers must quarantine, Chula Vista took emergency action to grow its pool of substitute teachers. When the district first reopened for the 2021–22 school year, Chula Vista was only able to secure half of the substitutes needed each day. To attract more applicants, the district increased the daily rate for substitutes and initiated a marketing campaign to recruit substitutes from the community, including parents with bachelor’s degrees. The school board also voted to hire at least one full-­time substitute for each school and to pay ­these teachers at the upper range of the substitute pay scale. As of September 2, 2021, half of the full-­time substitute positions had been filled and the district was able to find enough substitutes to fill in for teachers 70% of the time. Based on Governor Newsom’s August 16, 2021, executive order, which allows retired staff to return to schools without waiting 180 days ­after retirement, the district is also now reaching out to recently retired teachers and principals.

How Are Districts ­Handling In­de­pen­dent Study for Students Who Are Not Attending in Person?

To help maintain continuity of learning for students who choose not to return to in-­person learning and students who must quarantine, all of the examined districts have implemented an in­de­pen­dent study option, which is the ­legal vehicle the state is using this year for both long-­term remote learning and short-­term events that prevent school attendance, such as quarantines or natu­ral disasters. On September 23, 2021, the state of California enacted further updates to in­de­pen­dent study requirements, which clarify that districts ­will receive state funding for students participating in in­de­pen­dent study due to COVID-19-­related quarantine. For students participating for more than 15 days, districts are required to provide synchronous instruction, daily live engagement, and tiered reengagement for students who may not be succeeding in remote learning options. For ­those in a short-­term quarantine situation of less than 15 days, ­these features of in­de­pen­dent study are not required.

Yuba City offers long-­term in­de­pen­dent study through its Yuba City In­de­pen­dence Acad­emy, which provides daily synchronous instruction in grades k–3, daily live interaction and at least weekly synchronous instruction in grades 4–8, and at least weekly synchronous instruction in grades 9–12. Students enrolled in the acad­emy are guaranteed a spot back at their original school within 5 days of submitting a request to the district. When students must quarantine, they receive packets from their teachers and continue to access classroom resources through Google Classroom. If a ­family wishes to continue in­de­pen­dent study beyond the quarantine period, they are enrolled in the Yuba City In­de­pen­dence Acad­emy.

In Los Angeles, the City of Angels school serves as both an in­de­pen­dent study option and the online school of choice for the district. For short-­term in­de­pen­dent study resulting from COVID-19 exposure, students are able to learn remotely by accessing live synchronous instruction as well as in­de­pen­dent work. When individual students must quarantine, they have the option to access all of their classes for live instruction and complete assignments using their class’s digital platform. In the event that a ­whole class must quarantine, students complete in­de­pen­dent work when not participating in live instruction, which occurs for a minimum of 3 hours per day for elementary students and 30 minutes per day for ­middle and high school students. When teachers must quarantine, they continue to provide instruction virtually to their in-­person students, who also receive support from an in-­person substitute teacher (Figure 2).

In Long Beach, the district manages learning continuity for students in short-­term quarantine using Canvas, a learning management system that allows classroom teachers to connect directly to families and caregivers and keep students connected to their daily classwork. Teachers upload daily assignments, asynchronous resources, and links to print and digital resources that are available to all students; in many cases, classroom and intervention teachers also engage in individual outreach to students.

For families that prefer in­de­pen­dent study, students in Long Beach can participate in ­either a short-­term or long-­term Beach In­de­pen­dent Study Program, which is self-­paced but designed by a certified teacher. Students who choose this option must disenroll from their current school and enroll in the program. Each school has a designee who provides information about eligibility, and in­de­pen­dent study teachers are dedicated to ­indepen­dent study only. ­These teachers may or may not be from the student’s home school. Families can choose to transition to in-­person learning at any time; the district states that it ­will make “­every effort to ­re-­enroll students in their prior placement.”

In terms of scheduling, elementary students participate in synchronous instruction with a certified teacher for 1 hour daily with 2.5 to 5 hours of daily asynchronous assignments. ­Middle and high school students participate in synchronous instruction daily for at least 30 minutes. They rotate class periods throughout the week with 4 to 6 hours of daily asynchronous assignments, dependent on grade level, and they are eligible to take up to 13 Advanced Placement courses. Students receive an additional 15 minutes daily with a certified teacher to review their pro­gress and discuss their needs. Overall, ­middle and high school students must participate in at least 60 minutes of live instruction weekly.

How Are Districts Encouraging Vaccinations?

Vaccines significantly decrease the risk of serious illness from COVID-19 infection and are available for ­those ages 12 and up. On August 11, 2021, California became the first state in the nation to require full vaccination or once-­weekly testing for all school staff. Schools must meet this requirement by October 15, 2021. On October 1, 2021, California also became the first state to require vaccinations for middle school and high school students, once the vaccines receive full approval from the Food and Drug Administration.

Recognizing that vaccines are a crucial strategy for protecting students, staff, and their families, and that districts can play an impor­tant role in addressing hesitancy and increasing vaccinations, all of the districts are disseminating information about vaccines and how to acquire them. Several are also hosting, or plan to host, school-­based vaccine clinics.

In Yuba City, the district is partnering with Sutter County Public Health to disseminate information about vaccines and free vaccine clinics, including consent forms for adults and children and a “frequently asked questions” flyer for parents. Clinics are offered Monday through Thursday and on alternating Fridays at the county public health office; the county has also arranged free public transportation to and from clinics through Yuba-Sutter Transit, the region’s public transit agency. In Chula Vista, the district has hosted vaccine clinics for hard-to-reach populations in the community. Once vaccines are approved for children under 12, the district also plans to host school-based vaccination clinics for students.

On September 9, 2021, LAUSD became the largest school district in the nation to require vaccines for students ages 12 and older, when the district’s board of education unanimously approved the policy. The district is hosting vaccination clinics at ­every ­middle and high school, created a ­family vaccination hotline to answer questions from families, and allows families to upload vaccination rec­ords through the district’s Daily Pass.

To continue participating in in-­person school, LAUSD students eligible for the COVID-19 vaccine ­will need to receive a first dose by November 21, 2021, and their second dose by December 19, 2021. Beginning January 10, 2022, students who are not fully vaccinated ­will be referred to the district’s in­de­pen­dent study program. Students participating in extracurricular programs need to receive their first and second doses ­earlier, with deadlines of October 3 and October 31, respectively. Beginning on October 31, 2021, the district ­will require proof of vaccination for students wishing to participate in extracurricular activities. Students turning 12 must receive their first vaccination by 30 days ­after their 12th birthday and their second dose no ­later than 8 weeks ­after their 12th birthday. Students are exempt from the vaccine requirement only if they have a medical exemption or have been granted conditional admission, which is allowed for students in foster care, students experiencing homelessness, mi­grant students, students from military families, and students with disabilities. Medical exemptions for students can only be issued through the California Immunization Registry; personal belief exemptions have been disallowed since 2016.

How Are Districts Encouraging and Enforcing Masking?

All of the districts examined have universal masking policies in place. In LAUSD, all students, staff, and visitors are required to wear masks in both indoor and outdoor settings. In Long Beach, Cajon Valley, and Yuba City, students and staff are required to wear face coverings while indoors. District protocol for Cajon Valley and Yuba City states that masking while outdoors is optional.

In Chula Vista Elementary School District, students are only allowed to remove masks while outdoors and while eating. When students are pre­sent, all staff are required to wear masks, regardless of vaccination status. When students are not pre­sent, vaccinated adults are not required to wear masks. Reopening plans for both Chula Vista and Cajon Valley contain advice for parents on how to choose a suitable face covering for their ­children.

Yuba City leadership has emphasized the importance of masking, with Superintendent Doreen Osumi stating, “That’s why masks are so impor­tant. ­Because it allows us to keep students in school.” District guidance lays out Yuba City’s mask enforcement policy, ­adopted by the district’s governing board in July 2021. The policy does not exclude or penalize students for simply forgetting to bring a mask to school and was developed to show how the district ­will work with families to address mask refusal. Masks are made freely available on ­every campus for students and staff. If a student arrives at school without a mask, they are provided with one and reminded to wear the facial covering. On the first day that a student refuses to wear a mask, district staff call the student’s home to explain why masks are required. On the second, third, and fourth days that a student refuses to wear a mask, district staff continue to call home, and the student is quarantined to a location outside of the classroom, is physically distanced, and is provided with comparable grade-­level materials. On the fifth day, a student’s refusal to wear a facial covering results in continued quarantine and a parent meeting to discuss enrollment in in­de­pen­dent study. As of September 21, 2021, the district reported only one instance of mask refusal since reopening for the school year. The student returned to in-­person school within one day, ­after staff spoke with the student’s ­family and devised a plan to address their concerns by allowing the student to have periodic masking breaks, outside and distanced from ­others.

How Have Districts Upgraded Ventilation Systems and Ensured Airflow?

The use of outdoor spaces whenever pos­si­ble and improved ventilation systems for when students and staff must be indoors are critical strategies for minimizing exposure to viral particles. All of the examined school districts utilize outdoor spaces to the extent pos­si­ble, particularly during mealtimes, and advise buses to open win­dows whenever pos­si­ble. Chula Vista has also purchased canopies so that classes can be held outside.

Across its schools, Chula Vista has ­either upgraded HVAC systems or provided H13 True HEPA air purifiers for each classroom. Where pos­si­ble, Long Beach has upgraded all HVAC filters to MERV-13; new buildings ­will have MERV-16 filters. In areas where HVAC systems cannot accommodate ­these high-­efficiency filters, air purifier units are provided. LAUSD has leveraged federal and state funds to upgrade its ventilation systems, and Yuba City plans to optimize its HVAC systems using MERV-13 air filters, with filters replaced at least quarterly and more frequently if needed.

How Are Districts Conducting Symptom Screening?

All of the districts conduct symptom screening, though each employs a dif­fer­ent strategy. LAUSD requires daily health checks for all students, staff, and visitors before coming to campus. Individuals can answer health check questions verbally before coming to campus or use the district’s Daily Pass website to answer questions before arriving at school.

In Chula Vista and Long Beach, parents are reminded to monitor specified symptoms on a daily basis and to keep their ­children home from school if they are ill. Both Chula Vista and Cajon Valley include the San Diego County COVID-19 Decision Tree in their reopening plans to help parents decide when they should keep their ­children home.

Cajon Valley requires all students, employees, and visitors to undergo COVID-19 screening before entering school or district premises. Employees must pass through COVID-19 self-­check stations on a daily basis; parents or guardians who drop off their students by car must place a reusable student health questions card on the dashboard to verify that students have not experienced any symptoms. Students riding the bus are screened by transportation department staff before boarding.

How Are Districts Addressing Hygiene and Physical Distancing?

Teachers in Chula Vista continually model handwashing and hygiene be­hav­iors, and videos are emailed to parents to help continue ­these be­hav­iors at home. The district has modified its cleaning and disinfection protocols based on state guidance and evidence indicating that regular cleaning is usually sufficient to remove viruses from surfaces. The district cleans classrooms and common areas once a day and fully disinfects spaces when an individual with COVID-19 has been in the area within the past 24 hours. Cajon Valley maintains a similar protocol, cleaning frequently touched surfaces with a soap and ­water solution and using disinfectant only in situations in which ­there has been a confirmed case or if a symptomatic person is pre­sent.

In Long Beach, high-­touch areas are sanitized and cleaned throughout the day. Hand sanitizer, gowns, gloves, and cleaning wipes are readily available. Similarly, LAUSD lists frequent disinfecting and hand cleaning as core safety mea­sures and provides hand sanitizer stations at locations throughout campuses. Yuba City states that classrooms ­will be provided with hand sanitizer and disinfecting wipes, and students and staff are encouraged to avoid touching their eyes, nose, and mouth.

All of the examined districts specify that distancing between students ­will be maintained to the extent possible. In Chula Vista and Yuba City, students are seated apart in classrooms whenever pos­si­ble. In Chula Vista, schools also encourage distancing at lunchtime and during extracurricular activities. In Yuba City, distancing is maximized to the extent pos­si­ble when students are unmasked for eating and drinking, especially when indoors; when feasible, the district has set up multiple serving stations on each campus to facilitate distancing during mealtimes. Cajon Valley has published detailed guidance on how to distance students, including specific seating patterns on buses and for snacks and meals as well as markings on playgrounds to help maintain adequate space.

How Are Districts Communicating With Families?

Each of the examined districts has a COVID-19 dashboard posted on its website and reopening plan documents that explain the district’s strategy. Some of the districts have implemented additional approaches to engaging families and school staff throughout the planning and reopening pro­cess. Prior to the start of the school year, Chula Vista administrators communicated with ­labor groups, principal groups, parent groups, and ­others through town hall meetings. When engaging parents, district officials intentionally structured meetings to ensure parents felt heard, by allotting 15 minutes for district staff to pre­sent and 45 minutes for parents to share their questions and suggestions.

In Long Beach, the superintendent provides weekly video updates in multiple languages, including Spanish and Khmer, and appears in partnership with the county’s public health officer. All information is or­ga­nized in an accessible ­family guide that describes the district’s mitigation protocols. The district has also created a new position and hired a Chief Communications and Community Engagement Officer in July 2021.

Cajon Valley holds regular school site town halls and separate stakeholder meetings for teachers, parents, and classified employees, and holds special board meetings where students, parents, staff, and community members can make comments and ask questions. The district also provides its reopening plan materials in multiple languages, including Arabic, Farsi, Pashto, Spanish, and Swahili.

How Are Districts Attending to Students’ Social, Emotional, and ­Mental Health?

As students resume full in-­person learning, districts ­will need to attend to both their physical safety and social and emotional wellness. In addition to using advisories to cultivate students’ sense of belonging and offering engaging extended learning opportunities, Cajon Valley is attending to social and emotional safety in part by emphasizing the roles that teachers and staff must play to prevent “bullying, harassment, intimidation, threats, and knowingly making false statements related to COVID-19,” drawing on a resource put together by the San Diego County Office of Education.

To meet students’ ­mental health needs, Chula Vista is strengthening its ability to implement a multi-­tiered system of support (MTSS). In addition to hiring a new MTSS Coordinator, the district is spending over $3 million to place school psychologists in ­every school while also hiring more social workers. The 10 schools with the largest enrollments of high-­need students ­will have a full-­time social worker; the remaining sites ­will have a social worker who is shared with one other ­sister site.

During the first weeks of school, all Long Beach students participated in Smart Start activities that centered on relationships and student belonging. To address the trauma of the pandemic, Long Beach has also developed a detailed learning acceleration and support plan that includes the hiring of additional counselors. In terms of tutoring, the district is leveraging $1.5 million in federal funding to provide additional supports during the school day, ­after school, and on Saturdays.

Conclusion

Each of ­these districts, ­whether they have more than a year or just a few months of experience operating ­in-­person instruction during the pandemic, provide impor­tant models and key lessons for safe school reopening. As their work demonstrates, schools implementing multilayered mitigation strategies can stay open safely, minimize further disruptions to learning, and ensure that students can get back to the business of focusing on their learning and reconnecting to their school communities.


Reopening Schools Safely in California: District Examples of Multilayered Mitigation​ (research brief) by Naomi Ondrasek, Adam K. Edgerton, and Jennifer A. Bland is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

This work was supported by the Chan Zuckerberg Initiative, Heising-Simons Foundation, and Silver Giving Foundation. Core operating support for the Learning Policy Institute is provided by the S. D. Bechtel, Jr. Foundation, Heising-Simons Foundation, William and Flora Hewlett Foundation, Raikes Foundation, and Sandler Foundation. The ideas voiced here are those of the authors and not those of our funders.