Nine times out of 10 when a child says "I don't believe" they look at the parents and not the child so it's not an issue. You are the "nasty heathen" who hasn't taught your child any religious beliefs.
My nephews however are Jehovah's...and I do know they put up with shit from the other kids. Sucks, because they're good "normal" kids, when mom isn't dragging them off to kingdom hall every day.
My son's present girlfriend has devout Christians for parents...the first time he went over there for dinner they sat down for prayer and he felt like a deer caught in the headlights.
He came home and said "what do I do?"...I asked "what did you do?". He told me he just bowed his head, I told him that I normally do the same...mainly just out of respect for the people I'm sharing a meal with. He asked if he had to pray...I said only if you want to...he then asked have you ever prayed at a meal....to which I said maybe once or twice when I knew they were a really lousy cook and the evening wasn't going fast enough.