Seems like atheist in predominantly religious societies tend to behave a bit different, and I can understand that teenagers would want to make a big deal out of it.

My parents were atheists, and so have I been my entire life. But we still celebrated Christmas because it was nice and a tradition. We didn't go to church or do any religious stuff during Christmas, but ate a traditional Christmas meal, had a Christmas tree, presents and what not.

Religion was just not a topic at all, unless religious people did stupid stuff in the name of religion