I seriously doubt any of my Japanese high school or university students regularly experiment with alcohol in the same way as I did at that age. Those familiar with the near-permanent stench of beer in UK students' union buildings would be very surprised to discover that Japanese universities only very rarely have on-campus bars - and even then these are restricted to academic staff and perhaps their invited graduate student guests. Consequently, the 'experimenting' with alcohol that is a fundamental part of campus life in most European and North American universities just doesn't happen in Japan. Group drinking behavior only becomes the norm once you're employed. It's a ridiculous situation that Japanese students can't legally get binge-drinking out of their system before graduation.
A note about beer vending machines. These actually switch off at eleven o'clock every night. You can still buy alcohol at the local convenience stores. The law was changed a few years ago in theory to prevent high school students from purchasing beer. In reality, actually finding a beer vending machine these days is a task and a half - they are no longer a common sight. Furthermore, high school students are far more likely to buy beer during the early evening hours than they are to break their nine or ten o'clock curfew! Of course I live in a rural city so I'm happy to be corrected if it's a common sight to seen seventeen year-olds out and about at drinking establishments in Roppongi and Akasaka to the wee small hours.