My DS's primary seems to have a lot of problems with balls going over fences into neighbouring gardens and not being returned, so the extent that the staff limit the number of balls they let the children play with at break times. Some children take in their own balls, but my DS doesn't want to because he says some of those have gone over the fence too (sometimes thrown deliberately by the sounds of it).
How do other schools cope with this? Do they just keep replacing the equipment; maybe increase the height of their fences; send apologetic letters to neighbours requesting that they throw the balls back rather than binning/selling/keeping them?