When we as adults give advice to high school kids who are having a bad time at school, I think one of the ways it most easily goes wrong is that we make it sound like they ought to be able to do what we're suggesting, rather than making it clear that it might be useful to them if they could. The phrase I'm thinking of here is, "Don't let them bother you." Also, "Don't let them get to you," or, "What do you care what they think?" Of course it's useful if you can simply not care whether people around you are being hostile and nasty. But really, how many of us as adults can, by sheer force of will, make it totally not matter that we're spending forty hours a week with people who are willing to be as unpleasant as they can get away with? Not many. Not many of us as adults have to put up with that sort of thing. I have a friend who has recently left a bad job, a situation in which people were relentlessly hostile to her and to each other for her entire work day, five days a week. It was extremely hard on her, not because she wanted to be cool or wanted them to be her best friends evAR!!!11!!1!, but because she is a human being, and that kind of toxic environment is hard on anyone.
I think we should be careful to make it clear to teenagers who are having a bad time at school that we're not saying, "You should be able to do this; everyone can do this," but rather, "Look, we're focusing on you because you can't control the other person. We know this is hard for most people, but it's the best we can think of right now."
And you can't control the other people in your class. You really, really can't. And so fixating on "making them see" or "showing them" or "making them feel [whatever]," is not useful. The win condition is not that your high school classmates flock around you telling you how much they respected the theorem you just proved or the book you just wrote or the marketing decision you just made or the way you just handled your kid's tantrum. The win condition is that you can only remember the names of the ones who were kind and/or interesting to you. The win condition is that when you get news of something terrible happening to someone who smeared Ben Gay all over your friend's locker or pushed another friend down the stairs or any of the other lovely things that happened in high school, you are not glad. Because you're not just a bigger and better person than that, you're so much bigger and better and have moved on with your life so far that you had to stop and think why that name sounded familiar. That's what winning looks like.
So how do you move towards that win condition while you're still in high school? I don't know entirely; anyone with suggestions should feel totally welcome in the comments section. But I will note that the people I know who got through high school the happiest, healthiest people -- even if it was a good high school -- were mostly the ones who had other things outside school with which they strongly identified themselves. For a lot of them it was something computer-related, but that's probably a major skew because of the type of people I know. For me there was writing, and there was my piano, and both of those things were ways in which I could challenge myself and do interesting things that had nothing to do with school. I also had a bunch of pen-pals, which would probably translate to something internettish these days, but the point is, there were people who knew me and liked me and didn't care what so-and-so said to me in gym because they would only find out what so-and-so said if I could make it an entertaining story to tell them, or if I needed to vent. We stick kids in this environment and make it their major point of identity, which is disorienting enough at the end if the kids involved are in a good high school. When it's a bad one, we're strongly encouraging them to define themselves through something that makes them miserable. This is not healthy. It's not okay. And even something as simple as, "I'm someone who likes to go fishing with my cousins in the summer," or, "I'm someone who grows cucumbers," is a better way to identify oneself than, "I'm the verbal punching bag for Mrs. X's third period."
By the time you're in high school, having parents "put you in" a karate class or an archery class or a pastry-cookery class is not a good thing; if it's not what you've chosen, it's more of being shuffled around at other people's whim, which is not something you're exactly short on in high school. But sitting down and thinking to yourself, "What would be interesting to me apart from graduation requirements and college applications and dodging the jerks at school? What do I want to be able to do?" might be a good start. Everyone has to build a life that's irrelevant of the structures of high school eventually. Everyone has to find an identity that doesn't involve where your locker is or who you sit with in the cafeteria. No reason not to start as soon as you can.