If I understand correctly, it sounds like Croatia has a German-style high school system where one is either on a university-prep track, or on a vocational track.
In the United States and Canada, high schools are almost always a singular combined track, but after 10th grade, depending on whether one is intending to continue to college/university, they may choose more academic courses (e.g. pre-calculus, calculus, English literature) or more applied courses (e.g. applied math, communications).
The major exception is Quebec, where secondary school only goes to grade 11 (rather than grade 12) and students proceed to
CEGEP, which can either be a two year university prep program that consists of what would otherwise be grade 12 and 1st year college/university, or a vocational program of the student's choice, which might last up to three years.
Similar to your situation, it's free the first time, but any retakes or second programs would be at the student's own expense.
One other major difference I'd like to point out is that in the US and Canada, a bachelor's degree is usually 4 years (with a honours degree being 5). There are some jurisdictions that have 3 year bachelor degrees in the arts for those who are not intending to continue to graduate studies.