This time of the year can be stressful on parents, I get it. It is not easy on teachers either. Here's a few simple things you as parents can do to help out, and not be a dick to everyone involved.
If your family chooses to not have your kids believe in Santa, cool, that's fine, and that is your choice, but have a quick conversation with them that your family's beliefs aren't the only ones that matter in the world. You may not want your kids to believe in Santa, maybe it is against your religion, or maybe your kids are just older, but here is an idea, how about don't ruin it for everyone else, including teachers. Just take a minute to think how it effects others.
Picture this, you're an elementary teacher K-3, you deal with hundreds of 5,6,7, and 8 year olds daily, and there is five little turd kids running around whispering to all the other kids at recess and lunch that Santa is not real, and your parents are lying to you. Just imagine the shit storm that creates on a daily basis. Picture the pile of crap Jeff Goldblum walks up to in Jurassic Park and multiply it by 5. Except our pile of crap comes in the form of crying kids, kids arguing, angry parent emails, and fun phone calls all because you can't tell your kid to shut their yapper for a few weeks.
So in recap, tell your kids even if they don't believe, you don't have to ruin the fun for everyone else, including the teachers who are just as tired of dealing with your kids as you are this holiday season.