Yes it goes on, cheap vodka from Tesco though (used to be Bubbles when that sweet old couple were in charge). Some older teens do well out of being paid to buy it. However not all teenagers get involved and often when they do it is down to naive, or even downright negligent, parenting. The important thing is to talk to your teenagers and impose sensible boundaries on their behaviour to stop them being at risk, and don't assume they are not getting involved, in my experience it can be the most sensible geeky ones that get drawn in as moths to a flame to join the cool kids who then get them hammered.
I once went out on a Friday evening in summer to find my DC who had defied the ban on drinking in the parks. I saw some scary sights but by far the worst was on Moormead, mainly OP pupils but also other schools, including LEH etc. It was like a scene from Soddom and Gomorrah, many were very drunk indeed and disappearing into the bushes together with the obvious risks. There were also several other incidents of risky sexual behaviour, some involving the Police, amongst the pupils in West London schools (and probably nationwide), and some of those involved social media. You should not fall for the idea that their social media activities are private, you may be the only person not seeing your teen engaging in risky behaviour.
The reality is that teenagers indulge in risky behaviour in real life and online and it is our job as parents to protect them from the consequences. Schools also play a role and if you know there has been a gathering involving sex, drink and drugs or risky online behaviour do tell them . They can employ peer pressure from older pupils to mentor the at risk pupils as well as counsel the most vulnerable.
It tends to calm down in Year 11 as they mature and get too busy with exams......