[quote=@unicorgi]
But then we have to already know each other dont we? And it removes all the fun of getting to know each other and being new to the place
[/quote]

True, but a bunch of 1st years casting Wingardium Leviosa won't do much good for the action part of the RP. There'll be some prior knowledge, of course, but it's not like everybody has to be friends.

I second the 5th/6th year notion, 5th in particular because O.W.L.s. Standardized testing is always an interesting addition.