Vocal instruction is an art as well as a science. Every good voice teacher (actually, every good teacher of anything else) I've ever known or read about has their own unique way of teaching. All voice teaching, however, should lead singers to the same basics of vocal production. After all, the human voice in everyone operates by the same anatomical principles.
BUT- singers have unique strengths and weaknesses. I would coach someone whose voice was thin and reedy differently than I would someone who was hooty and hollow sounding. Teaching voice has to be a creative and co-operative team effort on behalf of student and teacher, not just a curriculum of "one fits all". And I learn new ways to communicate healthy vocal principles nearly every day I teach.
Here is the criteria for assessing a vocal teacher's method. it should make your voice feel and work better!! and initial improvement should be rapid. You should not leave a vocal lesson with your throat hurting. End of story.
Here are some questions to ask yourself: does the teaching help you sing with less tension? Do you have enough breath to do what you want to do? Does your throat feel better with less strain? Does it increase your range and your accuracy of pitch and give your tone more resonance? Does it give you more vocal endurance? Do you communicate better to your audience?
If the answers are yes, go with it. If the answer to one or more of these questions is no, be careful. But before you change teachers, be sure that you really understand what the teacher is asking you to do.
There is no substitute for personal vocal lessons and/or someone who is a real vocal producer in the recording studio. But there are good products out there that can help, cds and books you can train with (others as well as mine-I'll be commenting on them on future posts) which can be better than an ineffective or incorrect vocal teacher. No training is better than bad training!