Clubs and sports at Pumwicket work a little strangely.
Clubs are allowed at any time, started by any student for any reason, as long as you can get one of the main staff members to sign off on it. Once you do, and file it with Mafalda, your club is formed.
There's almost no money, of course, so you have to make do with what you have. But you can do anything you like that's not outright illegal. Simply create a page for it on the wiki, or comment here!
Sports are organized by a little-used rule in modern England (that I may have made up). Schools with a very limited number of students are allowed to have co-ed teams and join one of the standard muggle school leagues.
As a result, all Pumwicket sports that are competitive are muggle sports. There is definitely a football team and a swimming team; everyone who tries out gets on. (There is no pool, but there is a quiet inlet from the ocean nearby.) If you'd like to start any other team, let me know here! I'm happy to populate it with NPCs.
Wizarding sports are allowed as clubs, but with no school brooms, few charms to hide them, and the like, Quidditch is a very careful and tricky thing.