Just like the rest of us, teachers respond to financial incentives. Other things count as well, of course, but financial incentives do matter. I thought I’d illustrate this with a graphical factoid. (I say “factoid” because there’s nothing terribly sophisticated in my statistical analysis.) The graph shows the relation between the fraction of teachers in a state who have gotten master’s degrees and the extra pay that comes with a master’s.
The red line indicates that a 10 percentage point increase in the pay premium for a master’s is associated with a six-and-a-half percentage point increase in the fraction of teachers who get a master’s.