[aleph_minus_one]

As a mathematician, I say: if the kid is "somewhat mature" in mathematics, I wouldn't say this is necessarily a bad idea.

I honestly love to read mathematical textbooks that are quite above my current mathematical level and knowledge. It is brutal to go through and attempting to understand the material, but this is soooo rewarding.

This method of learning mathematics is clearly not for everyone, but if you are sufficiently motivated to go this way, and love the brutality innate to this method, I actually would recommend it.