Fyi: it’s called post secondary because, I think, UK calls it primary, secondary, and after that is post secondary.
Roughly what percentage of people go on to Gymnasiet? Is the next step University of some sort?
Basically everybody attends gymnasiet. Some programs are focused on preparing for higher studies, such as University, other programs at focused on a trade. All programs have a minimum core curriculum of math, Swedish, English etc.
Yes, the next step is University (or some other kind of higher education), or not, if higher education is not your thing.