My understanding is that the "grads" don't arrive until after the park closes to the public/resort guests. So it should not affect your crowd levels at all (other than possibly people staying away from MK that day because of early closing/no Wishes/Spectro, etc.........). As far as where they stay? Not sure about that one. Wonder if they actually "stay"? They may just get bussed to/from using their local school districts bussing. Or have they "officially" graduated already and it's not a school sponsored event? Around here (Ohio), graduation isn't until last week of May/early June.