After 11 1/2 years of musical training and many different teachers, I have compiled everything I've learned into one basic philosophy. First, every musician is 100% unique, and in order for them to be successful, they have to have individualized teaching. Some people like classical music, others don't. So it shouldn't be a big part of their lessons if they just aren't into it.
Some people love rock, so it should be a heavy influence in their lessons. What is key is that the student is choosing exactly what he/she wants to learn. If the student is shy, open to anything, or is not sure what they want to learn, that is when you provide lessons that are well-rounded. This gives the student several different opportunities to develop a broad appreciation. Eventually, whether they tell you or show you, students will become interested in more specific areas of music. Now you can craft lesson plans that fit their interests.
I also believe that teaching music isn't necessarily "teaching." At the end of a lesson, a student should not feel like they have so much to do at home to prepare for the next lesson. I don't believe in homework assignments. During the week, students should definitely practice as much as possible, but there is no penalty for not coming to the next lesson prepared. The lessons are not for me, they are 100% for the student. Yes, it can be disappointing when a student has obviously not practiced, but it is only their loss. My job is more that of a coach. I provide the students with the necessary tools to be great, and what they do with the things they have learned is up to them. I cannot play the instrument for them, only show them how to play it.