This would be called Cruel and unusual punishment by any court in the country. This type of confinement is sometimes used to torture people. If the room has the right padding and lighting the person can be subjected to sensory deprivation. Most people cannot take more than two hours of this type of treatment. I don't think the room is a sensory deprivation room, but it could come very close.
The teachers and others should have to spend a day in there prior to putting any student in one. As for putting a 5 year old in such a room, well I'd put the person doing that in one for about 5 years. A room like that could destroy a child of 5.