Yes, they will treat supernatural claims as reasonable, and expect you (and your kids) to treat them that way as well, at least in public, and condemn you (and your kids) for being rude if you (they) don't.
If you live in the United States, the odds are high that your child's school will do the same thing.
My suggestion would be that you teach your children how to operate sensibly in such an environment, rather than try to keep them out of such environments, but of course parenting advice from strangers on the Internet is pretty much worthless.
Yes, they will treat supernatural claims as reasonable, and expect you (and your kids) to treat them that way as well, at least in public, and condemn you (and your kids) for being rude if you (they) don't.
I actually do not think that is true. They will treat supernatural claims as reasonable, but would not condemn me for not treating them as reasonable. They might condemn me for being avoidably rude, but I don't even know about that.
We actually plan on homeschooling, but that is not for the purpose of keeping kids out of an insane environment as much as trying to teach them actually important stuff.
I do, however, agree with your advice.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.