As a teacher I have found there is always some child whose parents tell them there is no santa etc and sadly that kid usually ends up telling the rest of the class. I see no harm in santa, just a lovely part of childhood, my oldest doesn't believe anymore (obviously LOL) but she never thought I had "lied" to her about it, she embraces it still for her younger siblings. I guess its a personal choice but from what I have seen nearly all children do believe in Santa for the early part of their lives.