Why Does Teacher Pay Peak Late?

Adam Ozimek wonders: 

As Michael Petrilli points out in Education Next, teacher pay scales continually rise with experience even though studies show that only the first few years of experience increases teacher effectiveness. So for example, even though a teacher with 25 years experience is no worse than a teacher with 10 years experience, he or she gets paid a lot more. Consider the [above] chart from economist Jacob Vigdor, which shows how average teacher pay grades compare to doctors and lawyers.

In these other jobs pay rises rapidly with experience, whereas teacher pay rises much more slowly and don’t peak until age 55, even though the benefits of experience all occur within the first five years. As Petrilli points out, if teacher pay rose in a commensurate fashion with quality enhancing experience, then it would increase quickly in the first five years, and then flatten out, which by making pay proportional to quality would remove all of the incentive to lay off older teachers. This is not to make the case for lower pay for teachers overall, in fact you could do this whole thing in a revenue neutral way.