No school horses are not lowly. I respect school horses more than any other, putting up with all kinds of crap from riders who don't know what they are doing. They are the most respectable horse.
The reality is that as far as money goes, our school horses aren't worth anywhere near what the show horses are. The risk factor is very low, but there still is one and we have made the decision to not trail ride our extremely valuble horses for that reason.
About being a bad trail horse, my horse is extremely calm and I'm sure he would do ok on trails, but the reality is that he is meant to show. He was bred to show, born to show, raised to show, and trained to show. I can tell you that no matter what you think he loves to show. He gets to go all over the place experiencing all types of things. He loves to jump and that he does. He is in his element when he is showing. He is always ready to pop into the trailer in hopes that he is going to a show and is always waiting at the fence when I come, hoping I may take him out to jump and school him. He jumps every log he sees in the field because he just can't get enough. So, no I believe he is doing what he is meant to do and loves it.
As far as letting other people tell me what to do with my horses. I fully respect my trainer. She has much more experience and knowledge then I could ever hope to have. We pay her for her opinion and help and I am definitely going to listen to it.