(Summary of the advice linked above is make sure students learn mathematics beyond the standard school curriculum, which is not designed for the top students, and make sure the top students have a chance to meet one another and to challenge themselves with difficult problems that they can discuss afterwards. The site that provides those links provides many of the opportunities necessary, largely for free.)
Here is commentary by a Fields medalist on what successful mathematics education looks like over the long haul:
The problem comes from the teachers, who themselves don't really know the subject. They know it as a set of rules, and thus thats how they teach it. Get teachers who actually know the material and the problem will mostly solve itself.
A more practical solution would be to change how the books themselves are written. Math is taught as just a set of rules to be memorized. We've lost the fact that math was motivated by real problems that real people had. We need to teach it in a problem-analysis-solution manner rather than "here are some rules and now here are some contrived problems for practice".
