My son has friends over all the time, but we're always here and visibly present.
Sounds like ME. I always have a "question" to ask. Just to be able to pop in and see what's up. hee hee I offer pizza and drinks when I pop in. I always keep my eyes open.
For another reason, if these kids are drinking alcohol, WE can be arrested for it.
There is a really disturbing movie called "Kids" that deals with this scenario. It's about 10 years old.
It's shocking, probably should be X-rated, and is very brutal.
Basically, it follows some pre-teens in an almost documentary fashion, including one predatory boy who has AIDS and does not care.
It is VERY explicit, but I recommend parents screen it and consider showing it to their children --- I believe it may scare "kids" into avoiding this fast life.