The first show I ever stage managed was the final slot of my senior year of high school. Prior to that I had definitely been involved in every show in my HS career - whether I was acting, designing props, AD/ASMing (we usually gave these jobs to one person), helping build costumes, coming in for all-day Saturdays to build sets, or working on run crew, I was involved in every single one of them. We had to apply for positions on each show, and the director would consider applications and choose them. I applied to SM, and so did one other girl, who had only been involved for two years, but had only done technical work. She was a close friend of mine. I got the SM spot, and she ended up being offered AD and ASM. She was REALLY upset about it. She blew up at me, saying I didn't deserve the job because I was an actor, and hadn't really done tech before. Not just her... LOTS of people blew up at me, actually. It was a truly miserable time. But I refused to give up my job. I had earned it fair and square - the director received two applications, and she knew us both well, and she chose me.
It turns out... the show needed her as ASM. There were complicated scene shifts, and I would not have been good enough to coordinate it all myself. I needed her on deck. If we had switched jobs... well, I didn't want to because I had already AD'ed and ASM'ed before and wanted a different experience... but also, the show would have not worked as well as it did. I wasn't good enough to manage the deck. I called the cues and it was fine, but I know for sure that I would have been a disaster backstage, and the show would have been a big mess.
She was still pretty bitter toward me through most of the rehearsal process, but during tech I think it hit both of us how important it was for her to be the ASM.
We graduated a few months later and went to the same university... and by coincidence, ended up living on opposite ends of the same hall. We didn't spend much of the first semester around each other, but second semester of freshman year we were back to being best friends, and sophomore year we lived together.
This isn't really helpful because it doesn't contain any advice. But just... high schoolers are high schoolers. There are going to be conflicts. People will get over it. Sometimes you have to give up on the thing you had your heart set on, in order to keep others happy. Or sometimes you have to do what's right for you and people will be upset but oh well. If this conflict is going to create a toxic environment, maybe you don't want to take this gig. If it's more important to get the experience and you're okay with staying in a fight with this guy, possibly for a long time, then take it. Only you can decide what your priorities are.