Just kick their ass/asses.
Most kids are pussies. In 10th grade near the end of the year, I was at my locker and these two freshmen lil' bitches said something behind me when I was pulling something out of my locker, I dropped my shit. I turned around and I grabbed the closer one of them, and threw him against the wall. His lil butt buddy took off and ran. Then I realized what I did, and I was like an instant away from demolishing his ass. And everyone was staring >_<, I let go and he started walking off real fast, and said something, and I said bitch that's why your walking away...
It felt good as hell, and they were scared of me and didn't say anything ever again. =)