Just as a reply not an excuse to those who said out of control horse. There are those horses who work wonderfully at home and then bring them into a crazy show atmosphere and they become a fire breathing beast. Been there and done that.
I once had been working with a little mare who was calm relaxed hunter when I rode her at home(barn where she was boarded) and even rode her in a schooling show there. When we went out to a larger show, she became a ball of nerves, shaking and it was all I could do to just do a lot of small circles in the warm up while shouting "Excuse Me" "Sorry" "Coming Through" to the other riders who where all looking down their noses at me. We ended up scratching all the classes.
So now as I have learned from this I try to take my horses out to as many different places I can before entering a show. Of course this was not an option for me then, as I did not have a truck and trailer. (or even a driver's license)