You know, I really believe that much of the problem stems from having teachers almost as young as their students. I cannot remember a teacher I had in school that I wouldn’t consider a mature adult. Now they have ex-students coming back to teach in their own school when they are in their low twenties. These kids need to start out in the elementary school and not in their own high school or other high schools where there isn’t much age difference between the student and the teacher.
You're right, of course. The most difficult thing for young adults to do is supervise others who are only a few years their juniors.
The military has a technique for teaching leadership. They are in the business of making 20 year olds into responsible, caring leaders of 18 year olds.
The educational establishment lacks an analogous method or model of teaching leadership.
So age doesn’t have anything to do with it. Kids have always had crushes on teachers but teachers didn’t seem to act on it back then.