They are the general population, look around. Teaching no longer provides a stable middle class life in most areas. They live paycheck to paycheck, struggle to afford housing, feel crippled by student loan payments, and have little opportunity for advancement.
It's easier to be incorruptible by money when you already have a lot of money.
One of the big societal problems with pushing down wages for 50 years is that it makes society less ethical because people aren't comfortable enough in their finances. When people aren't comfortable with their finances, they are less likely to be able to quickly ignore unethical things that might help their financial situation even a little bit.
Quick example: You see a guy drop a $20 when stuffing his ATM withdrawal into his wallet. I would say, "hey bud, you dropped a 20." Someone else might just let him walk out and pick it up for themselves because it would help them a lot more than me.
Where I live schools are commonly for profit, so shareholders and bosses exert pressure to get higher grades.
It works, without the students learning more. Our universities are complaining that students arrive that can hardly read even though their grades say they are able to.
And yeah, we have standardised tests administered centrally so we can actually to some degree measure 'grade inflation' too, and know very well that employment/pay based on grading undermines whatever slim value grading would have otherwise.