They will have a class for grade horses, usually seperated by age and gender. In 4-H classes, it just goes by the member's age, not the horse. This woman that I knew and a friend of mine both had registered Paso Fino mares and they showed them at the fair. I can't remember what they showed them under...registererd performance mares?
Ughhh...I can't remember, it was so long ago. Anyhoo, hope this helps