Of course he doesn't do it at home... they NEVER do it at home!

That sucks that you have a school age child that you can't trust to go to the bathroom alone.

I would start treating him like a toilet training child again. He has to ask to go to the bathroom and you can go with him to make sure he pee's in the toilet. He doesn't get that independance back until he proves he can be a big boy.

I would also tell mom that you just can't have that kind of un sanitary behaviour. You'll give him a few weeks.. days... whichever you prefer... to turn it around and if he can't then he's out.