What the those boy did was emotionally abusing, and I am so sorry that you had to go through that. Some people just know the exact words to say to hurt someones feelings.
There is a little dilemma because I think telling someone would be a great thing, because I think the boys need a wake up call, but I also know that telling someone might have to result in telling about the self injury. Is there anyone in your school that you can trust enough with this.. like a school counselor.. who would also be able to take care of the situation while under the rule of confidentiality? You would not be making any sort of fuss, because you should not ever have to go through things like this, no one should.
But, I do see that your last SI was november 28th, so congrats on that!
I hope this all works out for you, I really do.