If you took a group of babies and said to their parents, “Today I’m going to teach them to walk,” their parents would think you were a crazy person and take their children away. If you took a group of toddlers and said to their parents, “Today I’m going to teach them to use the potty,” their parents would think you were a crazy person and take their children away. But if you take a group of 9 year olds and say to their parents, “Today I’m going to teach them fractions,” they think that’s normal.
Children learn different skills at different times because they’re individuals and they’re interested in different things. If they’re keen on baking or making change or working in the wood shop or something like that they may be ready to learn about fractions otherwise they’re learning about it in abstraction. It’s not going to stick. It’s going to jiggle right out of their heads. They’re going to retain it for the test, regurgitate it, and forget it. That’s if they’re lucky.
If they’re unlucky they’re going to do some of these things: struggle with it terribly, turn something they didn’t know about into something they hate, do poorly on the test, feel bad about their inability to do the work, meet with the disappointment of their parents and teacher, get laughed at by their peers or siblings, and develop a full-on mistrust of their own capacities, a desire to run away from challenges, a hardened heart, and the desire to explore, learn, and investigate will be deviated into the desire to just get a good grade and be done.
You don’t want this. Wait. Wait until the child has a legitimate reason to learn a thing. It will stick. The learning will come along faster and it won’t foster in the child the desire to appear to know what he doesn’t know just to escape the horror of not learning it when everyone else did.