I hated high school. Hated it. Therapy is absolutely needed and I really think you should talk to your parents about potential medication either an anti-depressant or anti-anxiety drug. As adults we forget how raw a young person’s emotions are. I remember being very emotional, but it’s been so long that I can’t resurface those feelings. Like the difference between remembering that it was painful when you broke your leg and being in pain because your leg just broke. Those are two very different moments.
You have to have some way of coping with being the quiet person. Are there any other folks that are general “outsiders”? Those were my people and they got me through the years. We were the outcasts and pretended like we didn’t care about anything (we totally cared).
Sometimes people suck. And people make themselves better by being cruel. I can’t tell you how to not care, but I can tell you that 4 years is both eternal and short. You are stronger than you realize; you need to figure out how to put emotional distance between you and your classmates and just get through this one day at a time. Do as best you can to get good grades, get into a good school (trade or college) and get the fuck out of there.