So, if a cognitive challenge—such as the abstraction in calculus—will destroy someone’s motivation, then we should avoid that challenge. This matches the assumption that we shouldn’t teach calculus when it would make students abandon math (or in other words, lose motivation).

The math teacher never raises the idea of teaching only certain parts of calculus, so this principle doesn’t apply.

The math teacher doesn’t claim that calculus involves exceptional effort, so this principle isn’t triggered.

The math teacher isn’t discussing what teaching strategies are more or less effective, but rather the question of whether to teach calculus at all—making this irrelevant.

This straight-up contradicts the argument; the level of abstraction involved in calculus is clearly one of the math teacher’s primary considerations.