Although I'm sure there are a lot of schools that come from further away and stay a couple of days probably a bigger percentage of the schools that attend Grad Nite,especially in bigger groups probably come from closer and don't stay several days at the hotels.My Grad Nite consisted of us leaving our high School in Miami around 1pm and driving up the Turnpike to get to Medieval Times for the dinner show at 6pm,we then left and headed to MK around 9pm staying until 5am when the event finished and driving right back to Miami.I've seen many other threads on this topic and the general consensus is that you will probably see some groups in the parks and hotels but it won't be overrun by them.