Need help ex bf being jack?

ok my bf and i broke up like 2 weeks ago and now he is going out with a 7th grader he is in 9th like me and so almost everyone knows now he has the nerve of asking me why i was startin rumors and i soo wasnt and all he keeps doing is blaming me and telling me he is going to tell the principle and i dnt know how to make him stop help plz