Perhaps get an upper-grader to hang out with him?
When I was in high school, there was a 10th grader that transferred to our school.
Right away, he started picking on the 9th graders, beating them up unless they gave him their lunch money.
The kid thought he was a badass until one day, I had about enough of his sh!t - keep in mind, that at the time, I was the school's varsity baseball pitcher also lettering both track and baseball. So *technically* speaking, I was a jock, so I had a bit of latitude when it came to getting in trouble.
So one day, I caught the guy in the hall, roughing up a freshman and I snatched the punk up by the hair and beat his ass and then stuffed him in the trashcan.
What did Mr. Tough guy do? He not only cried, but peed himself.
I was sent to the dean's office and got a stern lecture, Mr. Tough-guy was the laughing stock of the school and all of a sudden, I had little groupies.
* I should add that I was a senior (12th grade) and stood 6'1" and weighed about 185 lbs., too. *