I had a pre-calculus and calculus teacher in high school who spent most of her time bragging on how enlightened our school's calculus education methods were. This was remarked on all the time - we skipped a lot of stuff that was supposed to be bad ways of teaching, and we now permitted graphing calculators, and I don't know what all else was supposed to make it wonderful.
Now our school was actually a Texas "Blue Ribbon" math school, which means on some level we were considered to have a superior math education program. But personally I read all the material in our textbook that was skipped, and I helped a lot of my friends who were struggling - and I did it by reteaching them the same thing from different points of view until they got it, utilizing both the "modern" teaching we'd received in class and the skipped book material. (I believe at one point I even borrowed my dad's college Calculus text from the 1960s as well.)
For all the noise that was made about how great our teaching was, there were a lot of people struggling, and they benefited from hearing the "bad" instructional methods that we were bragging we were skipping.
My kids are homeschooled, and one of the first things I started doing when we made this decision was accumulating a math textbook library. The thought of being able to teach kids math myself instead of throwing them to the mercy of whatever educational fads are being bragged about in a few years was part of what made the homeschooling decision so appealing.