Every president since Eisenhower has talked about the need for more teachers, especially in certain rural and urban schools, and in subjects such as math and science. For decades, policies have been made and laws changed in order to recruit and train more and more teachers. But research shows we’ve been looking at the problem wrong, and that these efforts haven’t solved teacher shortages at all, but have created an oversize labor force with less training, less experience and high rates of turnover.

Learn more: Who wants to be a teacher?