My difficult child was in a theraputic day school program when he was younger. 8 students, teacher and full time counsellor in class. They had a "quiet room". It was utilized. It was destructive. Even when difficult child was acting up in class, that room escalated him EVERY time. Never once did he get put into that secluded room that he wasn't sent home afterwards. It was not only the least effective tool in their arsenal, it actually created far more problems than it hoped to resolve (and never did resolve).
I'm sure in some circumstances it might be a alternative. But I don't have an example come to mind. For non violent things, other approaches are needed in my opinion. And for violent behaviour, really more intervention and support is needed. Sticking a out of control violent kid into a secluded room is punishment, not a resource for support. Its a dicey situation if you ask me, with limited and very specific only usefulness.