Basically, at USEF recognized shows, the unrecognized divisions such as baby green or schooling might start around 2’6". After a recent reorganization, the green hunter divisions now are divided into 3’, 3’3", 3’6", and 3’9". There are also performance divisions at various heights starting at 3’, and the international hunter derbies include the highest jumps, with options well over 4’. Green hunters are restricted based on past experience, while performance hunters and derbies are open to all.
There are also assorted divisions based on restrictions related to the rider’s age or experience. Pony classes are divided by the ponies’ height, with corresponding age restrictions for the riders. Children’s hunters and junior hunters must be shown by riders under the age of 18, and juniors and amateurs nowadays can jump 3’3" or 3’6".
There are also many divisions at lower heights with different names, but since those are not USEF recognized divisions, the heights and specs may vary from one show to the next.
Lots of choices. 