There is a massive trust issue here. The teachers are in a position of authority over young people who are hormonally all over the place and as such should be protected and not exploited.
When i was at sixth form college one of my friends was having sex with his old high school teacher who was married and also male.
Another guy in our year was having sex with one of the female teachers.
At the time one was seen as a bit of a weirdo and the other as a real player. With hindsight I don’t think either were particularly advisable despite both being previously sexually active. Both, i know, continued for some considerable time.