Was that this film? .. anyone know?

I'm trying to find a film I saw ages ago and I can only really remember one bit.

Two boys in a flat on a council estate, watching something going on from a bedroom window. One of the kids being a bit squeamish about the number of flies on the windowsill, and the other telling him "they're not gonna *beep* hurt ya, they're only flies". I don't remember anything else, just that I should make a point of seeing the whole thing.
It's probably a long shot, but the tags lead me to this. Could someone please tell me if that was in this? Or, if you have any idea what it is from, could you please let me know? (I'd do the same for you, if I could)