I haven't done a group roleplay in a while and my friend just introduced me to this site so I thought i'd propose an idea.

16 years ago, a research facility test tubed 10 sets of twins. One twin was kept at the facility while the other was adopted into the real world. The twins at the facility were prodigies and excelled in anything from music to mathmatics. Most of the twins that were adopted were normal teens in the world. Now, the facility with the front of a boarding school invites the other half of the twins back to see how they will work with their twin.

There will be a limit on the number of people able to join. There are ten sets of twins. Someone can play your twin or you play them but there will be a 2 character limit. If someone doesn't play your twin, you play them by default and does not count as your two character limit. There will also be five teachers/scientists along with the headmaster/leader that will be played by yours truly when he is needed.

Edit: There will only be a character  limit after seven people. I also will play your twin if asked.