Sounds like the instructors have no idea what dressage is or how to teach it.
I find unfortunately that this lack of decent training results in injury and many times a serious dislike to a discipline they were never properly introduced to.
It does appear that Australia is extrememly lax about anything to do with this discipline as I hear stories like this a lot .....all from Aussieland.
Ummmm ok, Don't know where you're from but I can tell you, you don't see horses going nuts and leaping out of the arena as a frequent occurance in Aus. This was clearly just a riding school or pony club style event. Official dressage days are NOT like this. I find it very offensive that you pretend to know what goes on here, obviously the stories you've heard are from other lower grade events.
As I said above, I've had my horse leave the arena before, purely my doing, I had ridden the best test of my life, moments lapse in concentration with the arena was not shut up, riding a very marey mare with friends in the warmup arena and we're out.
I have only even seen one horse leave the arena where I am, and South Aus is probably one of the most casual dressage areas in the country other than NT and WA. There are a hell of a lot of excellent riders out here, we've had a few over in Germany and other parts of Eurpoe training, and also have received fantastic comments from overseas trainers coming over to conduct clinics.
Don't go around spreading your ASSUMPTION that Australia is all about badly behaved horses and riders with no education as this is simply not true. We've beaten the US and plenty of other countries in large scale dressage comps a number of times before and we'll do it again as the quality of Australian dressage continues to improve.