Three O'Clock High
(1987)

Jerry (Casey Siemaszko) finds himself sucked into a fight with a violent "at risk" student Buddy (Richard Tyson), who just transferred into his high school.  All his efforts to escape fail.  Finally, he offers money which Buddy accepts, but after Buddy calls Jerry a pussy, Jerry stands up for himself.  Jerry pulls off the fight of the century and puts Buddy down with Buddy's own brass knuckles. 

Jerry becomes a hero and the rumors about him are hilariously far from the truth!

Thanks Don P!