google "work to rule"
If two parties have already agreed that one will perform a certain amount of work and another will pay a certain amount of money, it is unreasonable for either side to demand more than what the other side agreed to.
A contract becomes meaningless if one side can arbitrarily adjust the terms.
Maybe that's a long winded way of saying that I suspect a lot of teachers are bleeding hearts and do not closely manager their time or monetary budgets closely.
That's not good for anyone.
Including software. It is also one of those reasons why the 40 hour work week is mostly a myth.