Besides, are you really arguing that a PE teacher and math teacher are doing the same work? Seems like two different things to me, that requires two different backgrounds.
The PE teacher and the math teacher are paid the same because they are in the same union, and they collectively decided that they would be better off having a few broad classifications and equal pay for those across the board.
Usually this is explained as giving management fewer points in which to drive a wedge to separate union members, and hence divide and conquor the whole collective bargaining unit.
Paying employees differently for similar work is pervasive and can be justified in several ways.
Calling it “cartoonishly evil” as a commenter did above is ridiculous.
If you don’t like this case, why not mandate a single uniform salary within or across firms?
Really looking forward to the inevitable comment from someone who will try to make a case for that wild idea.