But then Nathan moved into the performing arts section of Sybil Elgar's further education unit - and what people thought about his dancing, and his behaviour, was transformed. "We knew he was very good at imitating Michael Jackson," explains the school's FE manager, Madeline Sturrock. "But we have a professional dancer as tutor here, and Nathan learns all his literacy and numeracy through performing arts. Our tutor taught him ballet, tap and modern: whenever he showed Nathan a step he copied it and improved on it.
"It's quite amazing. He has the most fantastic charisma on stage. All his challenging behaviour disappeared when he started dancing. He'll dance to anything: he lives for dance. His tutor thinks that even if he was a regular student he would be good, not just allowing for the autism."
Now 19, Nathan is about to finish at Sybil Elgar. Attempts to find him a place elsewhere so he can continue dancing intensively have so far failed, although he is expected to do some dance at Redhill residential college, which he is due to join.
He has danced in Leicester Square, in the NAS's National Day for Autism, and at St James's Palace, for the Countess of Wessex. And the BBC is due to make a short film about him. His understanding and expressive language are limited, yet his dancing is not only expressive but flexible, says Madeline Sturrock.
"If he drops a hat on stage he will pick it up as part of the performance.
He just draws the audience in. People come to talk to him afterwards and are surprised by his limited responses because of what they've seen from him on stage."