Hi I used to post here years ago about my ds who had epilepsy, was non verbal and was presenting on the autistic spectrum. You guys were brilliant and gave me fantastic support and advice when he started school. 
He's now year 3 ands academically he is flying - top in maths, free reading and when he can be bothered turning out some great written work. He scored level 2s in his sats last year - telling you this to explain that there is no problem with his academic ability not to boast! (Although I am really proud of how far he has come!)
I have been called into school as he is being disruptive in class, generally being very silly and fidgety, not really getting that he is in trouble or that he's causing issues. He tends to react with a smile which makes things worse - don't think it's defiance it's just his default reaction but he is taking up a lot of the teachers time in trying to get him to concentrate and not disturb the lesson.
He is to my mind delayed in his emotional and social development and that this is at the root of the problem. I have a year1 dc as well and they are very similar in their behaviour while my year 4 is streets ahead in maturity.
He has access to a TA to keep him on track in class but it seems to be a losing battle. Unfortunately his 1to1 that he had in KS1 who used ABA with him is no longer at the school.
So where do I go next - meeting teacher next week to try to put something in place to improve things - what should I be looking at suggesting or is there someone I could talk to.
Any ideas will be great 