Depending on your child, and the room this could either backfire or work. If the room is calming, and he accepts it as such, and it is worded as taking a break, it may work. This never worked for us, b/c our son never bought into it and the stimulation levels were either too high or too low. They will not want it to be viewed as a reward b/c otherwise behavior will get worse so he can go there, so it is likely to be boring and confining. If it is where he can see interesting things but cannot touch them it may set him off.
Have they tried a calming "area" in the classroom in a corner with books or something relaxing? That worked for minor issues some of the time. When it got beyond that, and he got sent out of the class, behavior got worse.
YMMV