Franklyn Wang was a semi-finalist coming in 4th place in the 2013 Mathcounts National Competition, while scoring 16th in the 2014 Mathcounts National Competition. Franklyn Wang attends Harvard University.
By the way, this mathematician solved a 100-year-old math problem — in high school. Edit
Here is a quote:
"Before I began mathematical research, terms like cosets, Galois Groups and Irreducible representations all sounded like a foreign language to me when I was younger, but now feel as simple and natural as addition (okay, well maybe not quite as simple). Through this research, I realized that things are never so complicated as they seem."