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The teacher seemed pretty upset that she was being asked to make a change and plans to brainstorm over the next few weeks until our meeting. She still believes that at 6 years old there is not much deviation in math understanding depsite the fact that he can compute.

It sounds like this could be an opportunity to send in a workbook that has the appropriate level of math for your son. You could say "I found this and thought it may save you some of the work in making the changes we discussed." I'd try this approach rather than waiting weeks for the teacher to brainstorm when she seems to have underestimated his ability to understand math.