My teacher was good at making me behave. Not exactly my own teacher, but my first full-fledged gay sex was with a college professor.
I was studying in France (Junior Year Abroad) and joined the university choral club. It turned out that one of the older guys (the club was open to anybody on campus) took a shine to this 19-year-old American guy. So he kept winking and being friendly during and after rehearals - I was really new to noticing such attentions.
After several months, he eventually invited me over to his apartment a few blocks from the campus. It was the first time that I had actually been able to act both romantically and sexually with another guy in a mutually gratifying encounter.
He asked me to sit next to him on the couch and the sexual vibes were electrifying.. it wasn't but a few minutes later -- while we were looking through one of his photo albums that we just abandoned all pretenses, and started kissing passionately. Minutes later, he took me to his bedroom and then proceeded to instruct me in the realities and pleasures of gay sex. I got fucked in the butt for the first time by a guy who was about 40.
Unfortunately, he was not really interested in a relationship -- except jus sex from time to time. It was very disappointing for me and I learned my first 'lesson' about what can be the difficulties in maintaining (or establishing) a relationship especially because it was such a closeted time. His being a teacher was problematic for us both so he never wanted to see me on campus. Eventually, I gave up seeing him and before too long returned home.