I remember once reading a book about a boy who was for whatever reason summoned to this juvenile delinquency centre that existed outside the normal time frame and sentenced to remain there fore 300 years or so. The inmates do not age and when they return home, only a few minutes have passed
He then later breaks out, with his friends by somehow commandeering the time ship or whatever it is that they use to get in and out, although if I recall, one of them ends up being left behind. (I also remember there being a love interest between the protagonist and the one left behind)
I think I remember a couple details, such as the fact that the prison building was doughnut-shaped and movement between the parts of the building was over walkways in the gap. I believe the cover (of the paperback edition I read, at least) was also white tiled with something written on them in red.
I've been trying to find the name and author of this book to recommend it to a friend, and I can not find it, any information at all you may have would be invaluable to me.