That is a difference I'd not considered. The young man I mentioned was actually a young man - about 22 years old - but I've also often taught teens and older adults EFL. The teens I've taught have only been in summer schools and made up of many nationalities, so there was no way I would be able to know all of their swear words anyway. The adults I expect to act like adults (although the university students were often quite immature, swearing at a teacher is extremely poor behaviour compared to them having a joke with each other in their L1) and if/when they don't behave well their peers usually give them very little attention. I did teach English to children for a few years, in China and Korea, and I don't remember them ever behaving that badly (although it was quite a while ago). They tended to behave well, most of the time, in my classes although got fairly excitable at times. . In fact I don't recall this often being raised as an issue in TEFL, at all. We have more issues with commercially-oriented management, students' lethargy, phone use, poor chains of communication, and cultural differences. There's also an attitude towards TEFL; that it's always unprofessional and only staffed by unqualified backpackers who don't do a proper job. Fortunately I don't come across that very often.