For my senior trip last year, all of my friends went (there were 10 of us) and there were quite a few fights (but they were all caused by a girl we didn't like anymore). And we weren't all even sleeping in the same rooms.
And when I took my 2 bffs down to WDW for a week like 2 years ago, I did start getting a little sick of them after a while. It is hard to be in such tight quarters with people. Especially since you all are gonna be exhausted from doing the parks all day, staying up late, etc.
You'll still have a great time, but don't expect everything to be hunky dory and everyone loves eachother 24/7.