In other words, get the students to use what they have to learn to think, they will unheedingly learn and remember.This is more effective than rote-learning.
But these concepts are not impossible, and I was firmly convinced that every one of my students could learn the material if they worked hard and long enough.
Before that, and for example when I was at university, the dogma in the text books was that the vast majority of brain development goes on in the first few years of life and nothing much changes after mid-childhood.
Substitute teachers perform a valuable role, but the fact of the matter is they are not the classroom teacher who knows the kids and know where they are with their material.