That already depends on the type of skill being taught. Learning a new language, for example, has never been dependent on teachers and I think I've been doing quite well with purely self taught English, and that was before methods like duolingo appeared. My mother is living in retirement and has started learning languages as a way to pass time, she has learned enough English through duolingo to achieve a conversational level and she never had a teacher. Is it really impossible for more sophisticated AIs to truly replace language teachers in schools, and have students do things through a computer? and possibly replace teachers in many other fields of studies too. I'd wager most of the less advanced courses in pre-college stuff could do well with modern, computerized, interactive methods of learning. I don't think you could replace the interaction with a teacher for more advanced studies, though.