The way we have to do it at my school is that Boys' Bowling is considered a club, rather than an actual sports team. We had about 6 teams of 6 each (5 bowl each week). We sign up our teams in the local high school travel league, which is co-ed, even though we only allow boys to do it from our school. The reason is that when the girls bowl, all of a sudden bowling becomes a sport, with varsity letters and everything.