They tend to have stubborn dispositions and are difficult for children to control. Because they are too small for an adult to ride and correct, the ponies continue to get away with doing whatever they want. That can quickly discourage a child from riding. When riding in a group, should a full-sized horse kick at a small pony, it's quite possible the horse will strike the child, rather than the pony. For this reason, many people prefer to start their children riding on larger horses.
Larger ponies can make outstanding mounts for children.
Several examples include the Welsh Pony, Welsh crosses, Quarter Ponies, and POAs. Whatever the size of the rider and horse, look for balance in the picture you see during a test-ride. If the appearance is pleasing to the eye, the proportions of the horse and rider are probably appropriate. In searching for a horse, you will hear the terms registered and grade. Some horses are registered with a particular breed association, as their parents were.