It takes a lot of energy to teach. This is especially true when the teacher is also doubling as the cheerleader ("Come on class, you can do this if you try!") and the babysitter ("Joey, stop putting your mouthpiece up your nose."). Of course, the behind-the-scenes planning also takes energy, as well as after-the-fact bookkeeping and other paperwork. Therefore, teachers must carefully manage where they are spending their energy in order to make it the the end of their career (or the year, or the day) without getting too many grey hairs or having a heart attack.
Who is supposed to be doing the work, anyway? My policy is that the students should be doing 90% of the work during class, and I should only be doing 10% of the work. After all, I already know the music! My job is to do the work before I come to class, through studying the music and preparing meaningful lessons. The students should be responsible for learning, and I am consistently guilty with trying to "learn" them (do the learning for them, which is not possible!) by playing cheerleader, babysitter, student, and teacher all in one. It can be exhausting, and very frustrating at times - especially when the students show zero appreciation for all of this hard work that I'm doing for them!
The nice thing about being a teacher is that when the "game" isn't going in your favor, you have the power to change the rules. A fair teacher always changes the rules in a way that benefits everyone, not just themselves. One of the ways to "change the rules" is to put this responsibility of learning back on the students, which works more effectively with upper elementary students and beyond. In order to avoid lengthy philosophical conversation (a. k. a. "getting sidetracked"), I simply play the "percentage" game with the students. If I'm perceiving that I'm doing 90% of the work, I let the students know the score: "Right now I'm doing 90% of the work, and you're only doing 10% of the work. Let's try and flip that around." When they work hard for a few minutes and get something accomplished, I give them 5% ("Now it's 85-15."). But if they need to be refocused due to behavior, not following directions, or too much talking, I give myself 5 points and take 5 more from them ("Now it's 95-5.") Espeically with older students, they get it. They know the point isn't to get to 100% before the teacher gets there - the point is to start working harder so that they learn more and give their poor teacher a break. The verbal reward of hearing the score improve is a positive way to frequently remind students to continue working hard.