I'm not sure what you mean by "never took it as a subject". In the UK you study Biologly, Chemistry and Physics up to and including year 11 (16 years old). I don't believe you can opt out of those, along with English and Mathematics.
I wouldn't be surprised, however, to hear that what we did learn in those years was behind a lot of Europe/USA.
Right,ok, I wasn't aware of that. I'm just basing this on the experience with my own sister, who went to a British school at the age of 15 and immediately picked only the few subjects that interested her and didn't have to do anything else. By age 18 when taking her A-levels the school actually limited her to only taking subjects where she had a high chance of getting a good grade as to not accidentally lower the average for the school. So in her final year at school she only had like 3 subjects, where I at the same point at a Polish school had like 10 subjects.
Normally, people choose around 10 GCSEs (taken in the school year they turn 16, the school year starts on 1 September). They choose 3-5 subjects for A level.
For GCSE, "minor" subjects can be abandoned -- I stopped studying art, "technology" (design/engineering) and German (since I continued with French). At A level, the majority of students focus on closely related subjects (e.g. maths and science), which I think is the weakness of this system.
Harry Potter has essentially the same system (GCSEs = OWLs, A levels = NEWTs), this isn't something J K Rowling invented.
It's unfortunate your sister couldn't study more subjects. Parents who knew the system might have been able to push the school to allow her to study more, but I can't find anything online where parents/students are grumbling about this. (Again, Harry Potter has the same situation -- Prof. Snape says he only takes the best students into his NEWT class.)
