i love iea so much!! basic explanation is that you have a team your with middle school and high school, you go to a different barn with your team and show with a horse you haven't ridden before, you basically pick out of a hat. you get a short description like if you need a crop and spur and than show. for jumping cross rails- 2'6 you get 2 warm up jumps to feel the horse out a little that is unjuged than a course to show. for flat walk trot and walk trot canter you don't get a warm up at all and just show agian with the short description. it's so much fun and great to be around people who share the love for riding and around the same age!!
My university participates in IEA. It is very fun. They get it ride a bunch of horses and really test their skills. Really don't worry that they jump only smaller things most of the time or groundwork. The challenge is really when you have to draw a random horse out of a hat and without a warmup go in and show it. Most of the time the shows are very laid back and affordable. Really interesting to watch. I haven't participated yet but I hope to soon.