It was after PE, and us dudes are all in a locker room, changing back into our regular clothes. Our locker room is split into 2 sections in the same room. 1 for all grades like freshmen-seniors, the other section is for juniors and seniors only. Each section of the locker room has the lockers in horizontal aisles. I was a freshmen at the time, and a junior was in the all grades section as he had some buddies that were sophomores. I heard some asshat from the other side of an aisle in front of us yell dumb shit. I yelled in a different tone of voice than my regular one "How's your moms throat feel after choking on my dick" and I giggled quietly as I finished getting dressed. 10 seconds later, I started walking away from the locker rooms when somebody from that aisle i yelled shit at launched an aerial assault, and they tossed a milk carton over the aisle and it hit the junior in the shoulder and spilled milk all over him. And thats how I saw a sophomore get beat up by a junior in a locker room over a milk carton.