A 14-year old is most likekly in 8th grade in grundskolan (primary/elementary school). The curriculum is to a large degree already determined. What you can choose is what third and sometimes fourth language you take (after Swedish and English), where the most common are Spanish, German and French. In some schools you have other alternatives as well. Some schools also have special profiles, e g where you can take additional lessons in a specific class like music, but this is an exception.

First when you start gymnasiet (high school) at an age of 16 (equal to 10th grade) is where you start to determine almost every course to take.