You're making the assumption that teachers can afford the lawsuit or that they will be supported through the process.

But, they've not been supported through any other of the recent challenges so they have zero reason to believe the teachers union will have their backs or that liberal parents will either.

Ultimately, I'm not sure I agree with you that quitting en masse won't also be effective. In the end, if there are not teachers, there are no schools. There's a huge chunk of the economy tied up in education for most states. Definitely for the ones losing their shit over CRT. Maybe enough schools closing down and the subsequent hit to the economy that will create will do more to get them to back down than anything. They'll have to or lose it all.

You're also assuming that a racist will just come in behind the teacher leaving and happily comply with the censorships. If that were true, then where are they? Everybody knows teachers are leaving. Why is there still such a dearth of applicants?

You're also assuming that litigation will yield the result you want, because it's obvious to you that it's a violation of the first amendment. But look who's sitting on the Supreme Court and how the lower courts are also stacked. The SC is about to overturn Roe v Wade in a manner that will effectively reinterpret the meaning of 4 Constitutional amendments. There will be further fall out. And these are the people you think are going to stand for the First Amendment? That's overly optimistic.

Gotta admit. I see a lot of utility in letting the school system crash and burn. When racist and conservative parents lose half their income or more because the state sponsored child care they depended upon to be able to work or live their best life is gone, they'll be singing a different tune.