My son's class is a y1/y2 composite (5 and 6). They have 3 maths groups, 4 reading groups and several spelling groups. I think the top groups are working about a year ahead. Each teacher sets their own timetable (except swimming) and there are about 420 kids. Our teachers teach all subjects and specials themselves (including swimming but the pool use is rostered) and everyone has breaks together. There is, however no gifted programming of any kind. If I wanted him to do something with gifted peers I would have to pay for a private programme and ask the principal to excuse him for the day.
My HG child is only 5 and I have been wondering the same thing.