A few years ago, my D did two courses during the summer between freshman and sophomore year: Neuroscience and Genetics. Like SFrog above, my D loved her peer group at CTY.
In addition, the the Neuroscience class really resonated with her. The following three summers she performed neuro research internships at local universities in the Boston area. Her common app essay was about her interest in both art and neuroscience, and I believe this research and how she described it helped her a great deal in terms of college admissions.
She is now at UChicago, and she still feels that her peer group at CTY was a bit stronger than her college peers, despite UChicago students having some of the highest test scores anywhere.
