How do I stop my ex from harassing me?

To give background, my ex boyfriend is slightly obsessive, to say the least. He broke up with me after throwing a jealousy tantrum back in November 2023 (on my birthday, might I add), yet he still harasses me to this day. He's hacked and defamed some of my social media accounts, sent his friends to insult and harass me in person, and has also purposely thrown basketballs at my face in gym multiple times (we're in high school by the way, if that wasn't already obvious from his maturity level here). I've tried to just ignore him altogether and to report this to my school, but absolutely no action has been taken at this point. Anyway, as angry and annoyed this all makes me, I'm not too keen on revenge here, since that would likely escalate the situation further. So, for now at least, I'm just looking for advice to get him to move on and quit his immature harassment. Thanks!