Ever been in a city-centre pub in Brum on a Saturday evening?
Excited, underdressed kids on Bacardi Breezers - but no parents.
I once had to navigate a friend to somewhere more salubrious by phone (The Joint Stock near St Philip's Cathedral, if ever anybody is in the same predicament).
Wells Cathedral School has an interesting idea. It hires a Bristol disco Saturday mid-day, soft drinks only, and runs a coach there and back.