I think this is extremely difficult, and will depend almost entirely on your school district and/or the individuals there with whom you have to deal.
I have to disagree with indigo here- my kids were certainly talented in math, but the hypercompetetive-ness of the school math league and AMC contests was very off-putting to them, beginning in 5th and 6th grade. It was enough to keep them from participating. As a matter of fact, near,y all our school’s “enrichment” was in the form of contests, bees and other competitions, the results of which were usually broadcast to the school community- a real deal-breaker for kids who are bullied for being different.
By high school that had lessened (both the bullying and the broadcasting of achievement) and our kids did get some personal benefit from scoring highly on the AMC, even qualifying for AIME, but it was not enough to get them to overcome their strong desire to fly under the radar.
Their relative abilities stood out most starkly during elementary school (or perhaps they had not yet become adept at hiding their talents) but even there, the school had a strict policy of not accelerating, etc, so we looked for challenge and enrichment outside of the school environment. And that would be my advice, unless you have a willing partner in your district.
