In the U.S. they are separate classes. Like there was normal classes, honors classes, and gifted classes. Which has its own problems because some of the gifted students often were socially awkward. So someone parents would ask to get their students with mixed schedules, like some gifted classes and then some honors.

I only took honors classes but knew a lot of the gifted kids because sometimes they just mixed the classes. AP classes weren't a thing until grades 11 and 12. So really like in my elementary school there was 2000 students, and maybe 50-60 kids were in gifted classes. (Meaning they couldn't make up a full 30 kid class)

So even though I took classes like AP Calculus, Macro Economic, Physics, and European History and places very well like scoring at least a 4 on all those exams which would put me in the top 3% or so of students.. I never took gifted classes.

Maybe it's different in different areas