Most students can follow the steps. They can execute a procedure, produce an answer, and move on. But ask them to justify their thinking, apply their reasoning to an unfamiliar problem, or explain why their answer makes sense — and the wheels come off. The National Research Council called adaptive reasoning the glue that holds all five strands of mathematical proficiency together. So why does it get the least attention? This post breaks down what adaptive reasoning actually is, why it can't develop in silence, and the practical routines that build it in every learner — regardless of grade level or ability.