My son goes to an AMI accredited school with AMI accredited teachers only. In general parents in elementary rave about the school. However, we did talk to a few parents whose kids are in elementary that had the same problem with mathematics. Their kids weren't interested in Math and they didn't do as much as they could do. The teacher did try to push a bit and the kids didn't do no mathematics but they were easily one year below what they should be. One of our close friend who had that specific problem with his daughter solved it easily with tuition but complains that it shouldn't be the case.

In kindergarten (casa), there's a lot of structure with individualised work and a child is unlikely to have gaps in a specific subject. On the other hand, I think that in elementary with the stronger focus on group projects, it's easier for certain subject to fall by the wayside if a student doesn't particularly care for them.