Had a disaster of an afternoon. 4 yo DS was at his swimming lesson. He disrupted the whole lesson by repeatedly splashing the other DCs and ignoring the instructor and talking over her. He had to be separated from the group.
I wasn't there, but I can imagine it as pretty much the same happened when I took him last week. So this week happened despite a talk with him before swimming about how to be good at swimming lessons (specifically discussing splashing and listening), and a bribe of chocolate at the pool shop after if he did good listening, and also making sure he'd done lots that day specifically so he wasn't suffering cabin fever (which I thought might be the problem the week before).
He has selective hearing which would rival the most cantankerous of elderly aunts! He's been like this since he was a toddler - we even took him to audiology when he was really little (at the suggestion of the HV who came to visit when we moved) to check his hearing in case that was causing him to ignore us! 
But his hearing is fine.
As well as phasing his parents out, he often just ignores other people too. Our lodger often says hi to him, and he acts as if she's said nothing.
His behaviour had been pretty bad in general recently, and I've tried to look at what we can do differently. DP and I have been very busy this last couple of years, with studying encroaching massively on our family life and this has got to have had an effect.
We use time out, confiscating toys, positive reinforcement / giving tons of praise for good things, we have bribery with a sticker chart which translates into pocket money.I've started reading Calmer happier Easier Parenting and trying to implement the suggestions, but I guess it takes time.
He's a lovely child, good natured and bright. But big for his age, and when he's badly behaved I can see other DCs can find it intimidating, today he just wouldn't stop repeatedly splashing for example. He even splashed the teacher in the face last week. He thinks it's a funny game, I don't think he registers other people think it's mean. He knows it's not acceptable though. I don't want him to become, or be perceived as a bully 
I don't know what to think, I feel a bit defeated at the moment tbh. I feel sorry for DS as he's missing out. TBH I enrolled him for swimming as I hoped something structured but fun might help encourage him to listen. But if he does the same next week we'll have to quit I think. (We tried football group before and had to pull him out of that too as he disrupted the class to the point it wasn't fun for anyone - screaming, tantruming etc as he couldn't cope with not being able to do what he wanted i.e. play with the ball all the time. He was the oldest there and the least able to follow instructions).
I'm considering popping into the pool with him to apologise to the instructor. And letting him know it's his last chance or he leaves the group. (We tried bribery, that hasn't worked!) He did 3 lessons which were mostly OK, so he can do it!
To be clear, this isn't just about swimming - that's just one typical example of a much bigger picture.
Sorry for the essay! Any advice gratefully received.