Your pay is not due to your education level in this world. It's equal to your ability to demand it. Unions don't magically mean you have all the power in the world, it only helps to level the bargaining table.

My wife is a union teacher, and makes a six figure salary. She's hardly a victim, and it's all thanks to her union, and the work of many union members for decades prior.

It doesn't happen overnight, and that may be the problem your union teacher friends are running into.