Yeah, but that doesn't mean, that parents can't give their children a head start by teaching them stuff, that will smarten them up or help them understand stuff at school.

I remember my father taught me how to divide numbers and somewhat how to multiply them, before we learned that at school, with his own explanations. For multiplication he taught me indirectly, by making "number tables" with me:

    . | 1 | 2 | 3 | ...
    -------------------
    1 | 1 | 2 | 3 | ... 
    2 | 2 | 4 | 6 | ... 
    3 | 3 | 6 | 9 | ...
    ..|...|...|...| ... 

Up to 20. I used to bring them to school and teachers were discouraging, not realizing, what a great thing this was and what kind of insight it could allow a child to have into basic operations.

For division, he often said: "How often does one number fit into the other?" as a way of explaining that operation.

Ah and he also taught me about negative numbers, when other kids at school didn't even understand what that was supposed to be, and teachers still wanted us to write "not solvable", instead of the correct answer, which were negative numbers. How silly.

When the time came and we learned about division and fractions, I had an easy time to understand what the teacher explained, due to knowing an intuition about what division actually means. The hardest thing for me was not dividing numbers, but following that methodical procedure to divide in the written form, digit by digit. Something I had done in my head already, when thinking about that some number "fits into another number" only half, ergo must be 0.5 added to the number of times it fits in there whole. Only that I didn't realize immediately, that this written way of dividing 2 numbers was the same thing actually.

In this way parents can make school life and learning soooo much easier and less painful for their kids. Granted, I did seem to have a gift for calculation in primary school, but what was so casually taught to me by my father every now and then, helped tremendously. It wasn't even like strict hours of learning. It was just using chances to show me stuff.

From my mother I learned to actually pay attention how I write words. Initially, my spelling was only OKish, not great, until one day I somehow realized "Hey I just have to think a little and pay attention." and suddenly had good spelling. But this didn't come about, without my mother sitting down with me and complaining about my handwriting and also once or twice forcing me to do some writing. My handwriting is still no good though. Glad that didn't influence my grades. I write better Chinese characters, than German words, apparently.

If I had children, I would definitely try to teach them such things. Even if it is just how to look at something or what to pay attention to, or small calculation tricks. I would try to make their learning easier and offer support when they need it to learn.