http://amc.maa.org/amc1012/2011/stats/11AMC1012-grandstats.pdfOn the 2011 AMC 10A (a math contest), the average score and number of scores by grade were
10 70.5 35727
09 62.4 24410
08 81.3 05018
The 08 actually stands for "8th grade and below". There are far fewer students in 8th grade or below than 9th or 10th graders taking the AMC 10A, which is intended for high school students, but they do better on average. The same pattern is found on the AMC 10B and even the AMC 12A and AMC 12B, where the small number of 8th graders who take the test outperform the 12th graders.
When young students choose to try to their hands at something intended for older students, they outperform them, at least on the AMC. This pattern would of course not hold if the younger students were typical of their age mates. When gifted students think they are ready for above-grade work, they often are.
