Legally they might be able to take a teachers work, as long as it was done as part of their employment at the time. this is just an extrapolation of what would be normal in the business world.

That doesn't mean that a teacher writing a fiction novel would lose their copyright however. But if they wrote a book based on their teachers duties, that might be something they could lose control of.

They would never have a legal pathway to taking a students work, even if done in school, since the kids aren't employees of the school district. It seems that would make their new policy illegal.

I'm sure the lawyers will catch on to that if they haven't already.