What to do about child playing outside and knocking on our door??

Aimless

I've had this with kids knocking, who were, shall we say, a little wise beyond their years. And we live on a bus route and a road that becomes a rat run if the main road slows down or blocks.

I just always politely declined on his behalf... sorry, X is just doing his homework/about to have tea etc etc. They soon realised he wasn't allowed to join them. I was always a bit wary about letting them in, and eventually there was an incident where they and a few other kids were playing with the neighbour's kid and stuff went missing. Only little toys, but still.

And definitely agree on it becoming habit if you're not careful! We used to walk along with someone after school, every day you'd get, 'can I go to X's house'. After a couple of minutes mum would remember an urgent errand and disappear, to be gone for ages. In the end I started inventing places I had to be after school.

warehouse

OP, just say no.

No letting him in.
No letting your lad out as soon as he knocks.

It will lead to a world of pain.