I may be missing something, and this is not an attempt of mine to defend the instructor in question, but I seem to remember the age of 12, 13, 14 as being the age when I came into contact with the real world, including an abrasive context with adult themes. Yes, I was upset by them at first, but I was forced rather quickly to accept the reality of what those moments were communicating. Of course, any twelve year old in a public school system will already have a great deal of exposure with adult themes if only from peer conversation, and I for one am grateful that the educators took it upon themselves to help guide some of this exposure in a more directed manner, so that it could add wisdom and relevance to youthful understanding instead of allowing them to remain crass and unrefined as such themes often are in the minds of the early adolescents.
Seriously though, if a thirteen year old can use the "F" word 48 times in a single sentence (granted a run-on sentence), and knows the various correct terminology and uses surrounding the word, I really do not think that any exposure to adult themes in an educational context is going to be bad for him. But that is only my opinion, and I am speaking more from my experience as a youth and student since I do not have the credentials to speak as a parent. I am only trying to inform that twelve-year olds probably know a lot more about the adult world than they let on.