Doing a little more research using different search terms, I found a couple of local articles describing vandalism at school playgrounds. The stories mention that the playgrounds are open to the public after hours and weekends (got my answer, although in kind of a bad way :(.) Ironically, I used to take my oldest to this school when she was a little tyke and some idiot burned the playground down just a few days ago: http://www.ksat.com/news/23006644/detail.html
I guess that the schools would welcome families playing there to at least keep the knuckleheads away during the day.