I was enrolled in the 1960's in an antiquated system called "Cour Classique" in French. We had a strict curriculum, designed to produce priests, doctors, lawyers and notaries. The system spanned eight years, high school and college. We were given no options until the last two years. I got my B.A. at 19, and promptly joined the Canadian Peace Corps (CUSO), learned Spanish in two months, and taught physics (in Spanish) in South America.
Maybe his school scheduled classes so it was impossible to do a language and a science subject at the same time. For example I dropped History and also Geography in school because they clashed with Science subjects.