summer seems to be the traditional low attendance time, for obvious reasons.
However, as parent I would love to have the scholl offer morning classes for the kids in the summer (though I do understand that being in the place from 3PM to 9PM and on Saturdays and twice during the weekday mornings for a couple of hours for the adult class, there is no desire for the instructor to up his presence there, and lets face it, kids rather sit at home in their PJs and play video games...)