My school forced the unofficial dnd campaign I was in since DND is too "Violent".  But then a week later they decided to make a new campaign for 7th and 8th graders. I'm in the 6th grade and I can't join since I'm a 6th grader. All of the original members were in the 6th grade too. To me, this is madness and I think against it. Should I start my own somewhere else? I think the local library might allow it, but I'm really unsure since I'm a bit younger than most players.  

Wow that sucks. I would just keep the game going and find a new location. If your library will let you play there then go for it. Just remember they don't like loud noises in there so don't be too loud and be respectful.

What about playing at somebodies house? Either yours or one of the other players.

Are your parents ok with you playing? If so, I agree with Dohohjar, start playing at somebody’s house. You don’t need the school  

I’d be careful about it, though. The way you describe it makes me think someone’s parents complained, and that’s what got it shut down. So, if it wasn’t your parents, start a group at your house, and be prepared that a couple kids might not be allowed to join. If it was your parents, that’s a whole different conversation. 

My parents are completely good with it, I think It would be good with them. I don't know whose parents were mad about it though. 

It also might not have been anyone’s parents. In some places (please do NOT say where you live) around the US, there’s a lot of issues surrounding books being banned and what’s generally being taught in schools. It could be the administration getting nervous that someone was about to complain, and they tried to get ahead of it. 

At any rate, there’s no reason why you need the school involved. Just play at someone’s house. The school has no say in what you do there. 

I ran a group at the public library for all comers for four years.

Your school's leadership sucks.

I’ve played in every place imaginable. Game stores, high schools, middle schools, libraries, houses, even outside or in sheds.

Never before have I personally encountered resistance to D&D in a school, but it doesn’t surprise me. I firmly insist that you speak to an administrator. In this day and age it isn’t hard to do at all, so just go and get an appointment with a principal or vice principal. School is a safe place for D&D because it’s students, not adults at game stores, which I’ve done many times, but when you’re this young I don’t advise it. If you still experience this ban after speaking to an administrator then get some friends and play at your house. If you can avoid public places at first it is better, because privacy allows for growth and whatever loudness you want. Once you fee comfortable with the game then venture out into the game stores and libraries. Plus, the school year is almost over, so next year you’ll be free to join.

Home or the library are he best choices, remember that libraries often have separate meeting rooms with doors that can be closed to keep loud sounds out of the library proper. If your library is close to the school then it should be fairly easy to go there and play if you’ve cleared a regular time with the library staff.

I started playing LONG before 6th grade. We played at school (during lunch and while waiting for busses after school) and increasingly more at one of our homes as the years went by. I'm a huge fan of in person at the table play. But even though I'm older than a lot of new players, I adopted technology at a very young age. If in person play isn't possible, then by all means utilize technology to meet your needs. Discord has all the tools you need to play, including voice, video, text chat wherever you are (through the phone app), and relevant file sharing. Plus it's free. 

Then there are the multitude of VTTs out there. Two free VTTs that don't require also buying digital content are Owlbear Rodeo and AboveVTT. I like both, but AboveVTT has an additional big feature in that it connects directly to DDB, for characters, monsters, and uses all the images from the various monster books you as a DM have access to, as token icons. Fantasy Grounds and Roll20 are great tools, though will cost you some money if you're the DM, whether it's a subscription/key or content. 

Two tools many people use, but I will never because there are far better free tools I've already listed, are Zoom and Skype. But if that's all you can use to get started, do what you have to do. Whatever route you decide to take, there will always be pros and cons, even in person. Don't let someone else talk you into one way of playing over another. Be your own person, weigh out your needs, and make your own decision. Good luck, and have fun.

Yea .... if you can, bring down parents like a ton of bricks on this. You need to get like a handful of them, but really angry. Teachers wither up and shrivel away in the face of angry parents. Or at least, that's how it works here. Here being Denmark.