I was told not to teach him anymore because I do not know the Core Curriculum which his school relies on, and if I taught him multiplication, for example, any answers would be marked incorrect on an exam because of the methodology.
My response to this would be: That's fine, I have no problem with my DS receiving down marks for procedures at this stage, when grades don't really matter, as long as his multiplication is correct. As he progresses in math and in life, the specific procedure used will matter less and less than the results. However, you're likely to lose his respect as a teacher and authority figure when you mark his correct answers wrong.
