I just wanted to add that, if a child wants to learn something, teach them! If they want to learn algebra and the other students are just learning multiplication, figure out a way to teach that one interested student algebra! And if you don't know how to do it or don't have the time or resources to do it, help them find someone who can teach them. A child isn't going to ask for harder work unless they are truly interested and likely ready for it.
So many times we've heard, "It's great that your child loves math and is desperate to learn more, but she'll have holes; we don't think she's ready." But encourage that love and desire to learn more in every way that you can. An interested child will fill in the holes easily. And if it turns out that said child was not, in fact, ready to learn the new material, no harm done. The worst case scenario is that you've shown the child that you respect them and believe in them and will nurture and mentor them and encourage them in something they love and are eager to learn.
Why so many teachers tell children, "No, you can't learn that yet" is beyond me.
