Some of these kids my sister’s friends have aren’t too good with respecting others’ property

They like to play in and around my sister’s pool, but they’ve been mistreating the various floaties my sister keeps for her guests and they’ve been littering as well. My sister has noticed the way they were treating the floaties yesterday and nicely got on them about it twice. But this morning, when I showed up at her pad, she was telling me how she found paper cups and water bottles lying around where those kids were playing. I’d guess they’re about 6-8 years in age, so I get them not quite comprehending the disrespect they’re showing, but I hope my sister has had or will have a discussion with their parents about it. They clearly need a lesson in it.