DD and I had what I call the 'magic mirror' math discussion* when she was like seven or eight and she had no problem with it (it's all the lower level stuff like fractions and memorizing multiplication tables that she has issues with). If a child can understand something mathematically then they understand it. It's not like LA where The Scarlet Letter just isn't appropriate no matter how well a child reads.
* Solving for x, the = sign is a magic mirror, moving numbers through the mirror, etc. Really basic intro to variables.
