I have two children, at two different BSs, and drinking and hook-up culture is definitely not on the list of things they talk to you about over parents weekend. Both schools have gone through periods of excessive rule breaking while my children have attended, but we heard nothing from one school during that time (I believe they did send an email to the parents of the offending class, but kiddo was not part of that class), and did receive an email from the other school (kiddo was part of the offending class, but not part of the problem) explaining that they were essentially at their wits end with students making poor choices, and asking parents to help guide their children into making better choices.
I assume there is drinking and hooking-up at the vast majority of boarding schools, and high schools in general. I also assume that school administration does what they can to keep it in check, but none of them are actively working to eliminate it completely, as they likely know that would be an exercise in futility.
Having said all of that, students can certainly get through BS, or any other high school, without partaking in drinking and/or the hook up culture.