Aha. You say "he has marvellous skills compared to his 'rl'" when he's on a computer.
I can see exactly what he means, and why he's doing it.
Imagine being a child who's blind, and if you sit at a computer you can suddenly see, but you can't when you're not at it any more. Away from it, the world is a scary dark place full of surprises and unseen furniture and potholes to fall into, but whilst you're on it, you can see something at long last, you can do some things others can do, and even better than they can. How excited would you be? How relieved? How scary would it be if you could only 'work properly' when you're on it, and people won't let you be?
It's like that for a lot of children with an ASD, for example. Computers are exactly how our brain works. They make total sense to us. There's no eye contact, no tone of voice, no body language to decode. It's absolutely ideal most of the time. Away from it, the world can be a scary place where we have few skills to know how to make it 'work'.
He's desperate to learn, to 'see', to grow - and he's not being just obsessional and silly (which might be what the teacher thinks). He's asking to use the one tool that makes life possible for him at the moment. He doesn't understand how important the social skills are, yet.
Of course he can't use one 24 hrs a day, so he's got to learn ways to cope with the real world too. But it might need a plan with some experts working with him so that he can build his knowledge of the world through and with that computer interface over the years. Art? He can draw a computer. Science? He could work out the basics of computers. Literature? He could read or view books on the computer. Communication? He can learn about computers talking to each other on networks and how they transfer information, and use that skill to see if he can understand that people do the same thing using words and gestures. The knack may be to use his special interest to get him interested in everything else.
And the teacher is going to have to understand that this is all part of who he is. He's trying to help himself, not annoy people. He probably can't understand why others won't let him use something that works for him, but want him to use something that seems 'broken' to him (social ways of communicating information).