AMHA- yes. But I'm against this becuase you can't jump a horse until they are 3. Yet you can show in obstacle as a yearling and two year old. So its best if you are designing them to just leave them out. JMO.
A horse has to be two years old to show in halter obstacle in AMHA. I am OK with it. The jump in halter obstacle is usually shorter. There is a difference between jumping one short jump and an entire course of jumps that vary in height.