Footnote 1

Eva has used the fact that 3 + (1 + 4) = (3 + 1) + 4. That fact is an example of what is called the associative law: a + (b + c) = (a + b) + c regardless of what numbers a, b, and c are. I doubt that Eva has ever heard of the associative law. And although she certainly cannot state that law in its full generality, it is clear that she understands it.

Word problems and model making come first. It is a mistake to first teach children the abstract associative law with the expectation that they will then be able to apply the law to solving problems.