A typical public high school consumes around eight hours per day of a student's time, and this does not even count homework time. Sadly, a large proportion of this time is wasted. Much of classroom time is taken up with disciplining students, answering questions from students who haven't bothered to read the textbook, or explaining material so that students don't have to acquire good study habits. Usually, the only students who listen to the teacher are the ones who are good students anyway, and they would rather spend the time studying the book so they would have less homework. This "classroom method" of teaching is not new; it was invented by the ancient Greeks, and it worked well for them for a simple reason: they didn't have books! (Actually, they had books, but they were hand-copied, rare, and certainly not widely available.) We have had mass produced books for several centuries, and any student who can read can learn.
"Independent study" is the simple practice of a student studying from the books that are made available to him. The important role of a "teacher" is not to teach the book, but to choose the books and to assess the student's progress, encourage them, discuss topics with them, and assist in organizing time. Of course, teachers should also help students when they have difficulty, but this doesn't often happen unless the student is placed in a book that is too difficult for him, something a good teacher should be careful not to do.
Studying independently has a long history of success in education. Our use of it derives from Montessori theory and practice, where it is recognized for its efficiency, its depth of learning, and its individualization of curriculum. It was popular in Europe before government controlled education became the norm; and it is often used in graduate schools, where a professor will mentor a promising student. We use it with all our students and have found it a nearly ideal methodology.