What should i do about 2 girls that are harassing me?

so, i play piano for a 1st hour chior class because the teacher cant play. there are two girls in the class that i guess have issues with me. one of them messaged me on fb and told me that she was going to beat me up because i was spreading rumors about her that friday. i wasnt there friday because i was visiting a neurosurgeon. anywho, i told her that if she touched me id sue her for assult and get a restraining order against her. today we had a substitute and she left me in charge. well, these two girls decided to not participate so, i called them out on it. while walking to my 5th hour they were standing in the corner. they came up to me (while i tried walking away) and were calling me a ******* ***** and muttering other profanities. one told me that shed beat me up again. what should i do? i think theyre all bark and no bite, but if they injure me in any way id put out of dance and skating. so, what should i do now? my mom knows about whats going on, but i havent told her about today.