I have not been to DL on a grad night since 1981 - my own LOL. Between DLR and WDW, I think we all know any time you get a group of teens together you will see this kind of thing. Whether it is the Brazilians on school break or cheerleader crowds you tend to see high energy teens not appearing to care about how their behavior and language and noise (screamy teen girls) affects others.
I have seen all of this on normal Disney days that are not grad nights. I also have heard profanity from adults as well. And other types of rude behavior from adults.
If I were going on a grad night I would follow the advice of the PP who mentioned trying to focus on dining or shows in the evening. Maybe that is the day you skip a typical afternoon break and power through and then leave the parks early.
Good luck to the OP!