i would demand to be fair that they make male only classes...i know its not what you want, but if they think they will have to start having to pay for use of a room and an instructor 3 nights a week for just 3 men, they may change their tune.
to be honest though, i think perhaps they should have some single sex classes... we have separate loos, we have have separate swimming, and lots of things so why not this? i would imagine for some people theyd prefer not to excercise in front of the opposite sex