Thank you for asking such an excellent question! Although I cannot speak much about the other schools, I can say that Cheshire Academy would have all that you are looking for (and more).
We offer the IB Diploma Program, and also IB certificate programs which allow each student to select the courses AND rigor level that would be the best fit for them. All of our students, and especially those from China, go on to excellent colleges and Universities including many in the Ivy League, UC system, Vanderbilt, or Johns Hopkins.
In terms of snowboarding, we have a mountain (Mt. Southington) that is about 15 minutes away and skiing/snowboarding is a Winter Activity if you so choose. While the mountain is small, it is closeby and they produce their own snow, so it would allow you to snowboard 3-4 times a week if you wished.
Please feel free to contact me at email@example.com. I would love to put you in touch with one of our current students (or recent alumni) so that you could hear from them what makes CA so special.