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But the students aren't supposed to know that yet. That's literally two topics later in the Common Core Standard, so they won't learn that for another day or two. Smh.

http://www.corestandards.org/Math/Content/3/OA/

Punishing students who are ahead is an excellent way to make all students equally disinterested. (Oh, but not equivalently disinterested.)

The question is whether the student knows about commutativity of multiplication or if he/she didn't understand what was taught or made a mistake.

Personally, I think the problem here is that math is taught as processes rather than as concepts.

It actually even did not matter here if multiplication is commutative or not. The child had to apply the repetitive addition strategy and so he or she did. Just probably not with the taught convention.

+1. In few years this kind of answers will be criminalized.