I agree that it's a bit short sighted to make 14 year olds give up on subjects entirely. I am very oriented towards social sciences, I would have given up all math and science type classes. Instead, I took 7 years of math in 4 years of high school and I'm really glad I did. I ended up liking math a lot more by the end of it than I started out with. I never would have been motivated to do it if not for the motivation of college admission. Because I worked really hard in high school and passed a slew of AP tests, I never had to take a math or science class in college.
By the end of sophomore year (about the age at which students take the GCSEs), counting HS classes took while in middle school, I had taken 4 years of HS math, 3 of Spanish, 2 of science, 1 of French, 2 of history and 2 of English. That pretty much more than fulfilled my state's academic requirements for graduation in everything but English (4 years required, no way to get ahead) and history (3 years required, also no way to get ahead). I'd put my last two years of high school up against any A level course load. My easy electives senior year were French III (I was also in AP Spanish) and a class that basically amounted to 20th Century History. But I could have just as easily taken nothing for two years but English, history (junior year), gym and advanced basket weaving (or whatever) and gotten the same diploma. So I understand why US diplomas are underrated.