Great points! I agree these aren’t perfect measures and I sincerely hope that this doesn’t come off as some hit on teachers. I just see this as an open empirical question that some economists — or more industrious Medium writers — can explore. Namely, whether increases in teacher pay will make it so that many of the current people teaching might be pushed out of teaching from greater competition for those jobs. You could also reframe that as whether increases in school performance that come along with increases in teacher pay come from the fact that schools are getting better teachers or because existing teachers are better when they are paid more. And while I take your point that the teachers from Equity project may have been getting more responsibilities along with their teaching. And I agree that this may confound parts of my argument, the main point still stays — the improvements in school performance came along with significant new hiring and forced resignations which presumably means that gains weren’t seen from existing teachers performing better because of better pay.