In addition to the safety and disruption concerns other posters have mentioned some schools have a no latex policy because of allergies. Mylar balloons don't have the allergy and safety concerns of latex, but still disruptive. My sons' former elementary school doesn't allow any sort of outside celebration brought in--no cupcakes, treats or anything of any kind. The teacher acknowledges the birthday at morning meeting (and depending on the age, might have a paper "crown") and the child goes to the principal's office to get a birthday greeting and birthday pencil. Kind of weak, but I was o.k. with that because it made my life easier (teacher's life easier) and I was tired of all of the sweets and treats being brought to school. At our middle school they used to allow parents to decorate the kid's locker, but I haven't seen that lately so maybe that's gone too. I had only seen this done for girls. My boys wouldn't be into that. We make a big deal out of birthdays at home, often celebrating for a weekend or even a week, so they don't seem to mind the school policies.