My son Grew out of it.

I've been there with my son at the same age. His nursery took him away from the play area when he did it and in time he realised that that behaviour had consequences he didn't like (toy and play area were taken away from him). Is he on any medication? When did he start this behaviour, ie. after vaccination? Have you tried biomedical food supplements? ABA also helps: you need to see what prompts this behaviour, it could be anything, but if you know what it is you might be able to prevent it.