I can really emphathise with this issue, my eldest is at secondary school now and my youngest moves up in September. A few years ago though, weekends/school holidays would be like this -
The kids in our road banging on the door constantly asking our kids to play out, which would last 20 mins at most before they were asking to come in. Then I'd find every room was taken up, screaming, shouting, hurtling down the stairs in cardboard boxes, (the neighbour's kids, not mine!). I did put a stop to that!
They would also be constantly pestering for snacks and wanting to use the computer, then insisting I phoned their parents for their Moshi Monsters etc passwords. After one occasion where my kids were locked out of their computer games through their friends repeatedly trying to put their own details in I stopped this!
Saying No to them coming in didn't make much difference really, they'd then set themselves up in our front garden with their arts and crafts stuff etc. My direct neighbour's ds who was in his early teens would come out and deliberately wind them up, so the other kids would come crying to me and I'd then have THAT issue to sort out
Once I was just getting in shower when they knocked, I heard dd answer the door and say they weren't allowed in, but when I came downstairs dressed they were standing in our porch way, watching TV through the crack in living room door!
The boy said he didn't think I'd mind as they weren't actually in any rooms! I couldn't believe the cheek of it!
It's all a lot calmer now thankfully, but what got me was that you hardly ever saw another parent supervising, they just kept sending them over to us. I was often exhausted by the other kids, and resentful of the time I could have spent with just my own kids after a busy week at work, taken away. So I can really sympathise!