1. Project STAR was an experiment designed to test the effect of class size. The experiment found that students assigned to small classes earned $4 more per year. If you add demographic controls, students assigned to small classes earned $124 less per year. (more)
2. You can use Project STAR's data to (non-experimentally) test for other effects. When you do, almost all measures of teacher quality fail to increase adult earnings:The few other observable teacher characteristics in the STAR data (degrees, race, and progress on a career ladder) have no significant impact on scores or earnings.
3. There is one measure of teacher quality that does matter: Whether the teacher has more than 10 years of experience. Chetty et al. find that students assigned to a kindergarten teacher over this experience cut-off eventually earn $1093 extra dollars per year. But bear two reservations in mind. (a) The t-stat is only 2.4 - extremely low for a non-experimental test with 6005 observations. (b) If you measure experience in years, rather than using their binary "more than 10 years of experience" variable, the point estimate is a statistically insignificant $57 per year.
4. Teacher experience only matters in kindergarten:The effect of teacher experience on test scores is no longer statistically significant in grades 1-3. Consistent with this result, teacher experience in grades 1-3 also does not have a statistically significant effect on wage earnings.
Tuesday, November 1, 2011
What does the data say about the importance of teacher quality?