They're called shag bands! Were big when in primary school when I was about 10. I don't think we even knew what 'shagging' was then.... Made a comeback a couple of years ago....
If you ban it, they'll just find something else. If you don't, it'll fade and they'll find something else. Either way, the teens will keep having sex because, for some odd rason, kids are out of their fucking minds these days and think they're 10 or 15 years older than they actually are.