So how about change the word from isolation to sensory break? Alone time? I now realise that as a child I used to really avoid the rowdy parts of the playground. I used to walk right round the school, observing everything that was going on, quite happy not to have to talk to anyone. Then on my walks I found two other girls who used to meet in a tucked away corner behind the science lab. That eventually became a haven of joyful human connection and a rich deep friendship.
What purpose is sought by isolation? If it’s punishment, ten it’s cruel. If its to give the class and teacher respite from the child’s exhausting behaviour, then a conversation with the child, in a no blame climate, can be had. See the super work of Michelle Marcia winner on http://www.socialthinking.com