Deanna M. De'Liberto long posting raised quite a few good points. It deserves careful consideration. Without going into all her points I would offer this one observation for your consdieration:
We -- mathematics teachers at all levels -- learned well and succeeded by being taught by the lecture method. It's very efficient: the teacher lectures, the student wants to learn what's being lectured about, he/she studies and asks questions about what he/she doesn't know, the lecturer answers the questions (by lecturing) etc. etc. Some people can learn this way and we are them. We like to teach that way because we learned well that way. It's difficult for us to consider (even as a point for discussion) that this may not be the "best" way. But we are not everyone. The second sentence in this paragraph contains a lot of assumptions which just do not apply to the majority of high school students in math or many other areas.