I guess I see where your school is coming from, but I think a detention is pretty harsh

I'm not a believer myself, which means i'm not convinced that some higher power created the earth from magics. Having said that, Christmas is the day that we celebrate Jesus, Yahweh or that one guy, being born. Saying that atheists can't celebrate christmas is like saying that every christian has to go to every single church service.

And this guy telling you to make your own holiday is really ignorant.

This is just my opinion though