Yes my DS does exactly the same. He goes a whole day at school without weeing, nearly every single day. Even when we go to the park after school, he'll not wee until he gets back home.
The same for poo. I actually have to tell DS when to poo now, because he can't tune into his own body.
He was OK with poo-ing before school, he's always wanted to be in real private, but could tell when he needed to go. Now its like he just doesn't seem to know/realise.
It drives me crazy because the whole needing to wee thing makes his behaviour chaotic.
I think it is very usual and lots of kids do this. But I don't want to ignore it. However I don't know what to do to make things better.
All I do at the moment is remind DS to wee at school everyday - and often this helps. And I tell DS to do a poo every evening before the bath and then he does.
Not sure if this is good/bad ... if I see DS jiggling about I say to him 'you can't have such and such (if he was about to eat something, or play with something) until you've gone and done a wee.
Again, I'm not sure if this is good practice or not, but it makes me feel relieved when he's gone, and I'm sure he feels relieved too.