Ultimately, 80 top teachers took the bonus and switched schools. In their new jobs, though, these teachers’ performance fell from the 85th percentile districtwide to the 66th percentile. (And for stats nerds, no, this probably wasn’t just regression to the mean.) So what happened?
“Teacher effectiveness is dynamic,” says Matthew Kraft, a Brown University professor and coauthor of the new paper. “Teaching is a team sport.”