i think you're going a bit over the top here. My daughter and many of the children of friends attend the Grammar and to use the phrase "human detritus" to describe any school kids is way out of order.
In fact I live quite close to the Robert Manning School and apart from the odd isolated incident, I don't recognise the picture you are painting of school kids today. OK a bit of smoking, swearing, dropping litter and the odd scrap now and then, but as Jane says, kids have always been like that. I don't think it is that much different to when I was at school nearly 30 years ago.