I'm good enough, I'm smart enough, and doggone it, people like me!

In case you didn't already know this, my oldest is a really smart kid...and I'm not just saying that because I'm his mom...he really is! He knows about things that I have no clue about, and I'm not talking about toys and games either. I'm talking about real stuff like how things work, and where things come from and all sorts of scientific stuff! He also can read like me, where you can completely tune out the real world and enter the world in the book...but he can also remember everything he has read, down to the tiniest detail. But it absolutely frustrates me to no end that he doesn't realize how smart he is! There are days when he can't (won't?) even do simple homework without a struggle or a fight or him saying "I can't do this! I don't know how!" when I know he can, and he does and is perfectly able to! We have given him no reason to think that he is anything less than brilliant, especially with school things and he has had some amazing teachers at school so they haven't either...where does that come from?! Maybe from just being the oldest and the personalities that come with that...I know I felt that way for a long time (sometimes I still do!) and my parents are amazing too. So my question is this: what else can we do as parents or teachers to make our kids realize that they ARE good enough and smart enough to do anything?