When students return to school in the upcoming weeks, many will enter one of the more than 100,000 classrooms across the country staffed by an instructor who is not fully qualified to teach. This is because many districts, facing ongoing teacher shortages, are hiring underqualified candidates to fill vacancies. While shortages tend to draw attention to recruitment issues, a new report, just released by the Learning Policy Institute (LPI), finds that 90% of the nationwide demand for teachers is created when teachers leave the profession. Some are retiring, but about two thirds of teachers leave for other reasons. Addressing early attrition is critical to stemming the country's continuing teacher shortage crisis.