ADHD - late diagnosis y6?

[longtallsally2]

DS2 was, until y4, a lively, happy, chatty, apparently typical little boy. He's bright, above average, doing well but wasn't achieving amazingly.
In Y5 he had a new teacher and his grades improved enormously - 3 levels up in the first term. However, his behaviour crashed. He was 'way too lively', unpredictable, rebellious, resentful of discipline and the teacher in particular, but he couldn't say why. She was new to teaching and puzzled by him too. We worked with her on a variety of strategies to enable him to cope with the day to day expectations of school. Her parting line was that he was lovely but some people are just not suited to school!

Back to Y6 and he seems much happier, much more settled, involved in a whole range of activities, with a lovely supportive teacher. His work interestingly has slipped in standard/grades, but he is happy going to school and we are pleased to see his confidence grow. Until today. I've just got back from the Christmas show, in which he was given a key narrator’s role. I cannot believe how he behaved. It wasn't bad as such, just . . . .extreme. Whilst everyone else stood and sang their part, he chatted/gave a running commentary to his neighour, danced, wiggled . . . think Jedward, in a nativity! In between he performed his role extremely well but I was sooo upset. Fortunately he was in the back row - maybe not too many other parents were aware of him.

But I am so upset - because it seems that when he succeeds at something, then he self destructs. And is happy to distract from others' achievements. Which doesn't seem a good pattern for life. Does this sound like ADHD? Is it possible for it to set in late like this? My inclination is to now ask for a referral/assessment for him, ahead of secondary school - and we could potentially go private if necessary - but your reactions, experience and advice would be very much appreciated.

[lljkk]

Puberty changes the brain and can bring on a lot of changes, but he seems rather young for that.
I've known people who didn't get a diagnosis of ADHD until this or later age (including guy whose sister had had a diagnosis for yrs before that).