I'm actually so thankful that in my middle school years social media wasn't such a big thing yet. We had facebook and that was about it.
To me its very disheartening to hear stuff like this because I remember when I was younger, I was often stressed and afraid that bullying would go beyond school. Now these school bullies can pretty much have access to you 24/7 via social media.
If you have proof of them sharing your dick pics then you could honestly probably land them in some serious trouble. If you want revenge and have nothing to lose, just go to the police with your proof.