Now this one might get me in trouble... In regards to schooling shows, I would like to give my 2 cents about turnout. I might get those 2 cents flung back at me and I might get hit in the forehead by a flying penny and have to walk around with an Abe Lincoln imprint on my head for a while, but I will take that chance!
A schooling show is a practice show, not a casual Friday show. There are some shows advertised as "fun" shows and jackets, etc. are not only not required, sometimes not allowed! However, unless it specifically states that on the entry form, then a horse show, no matter the level, should be treated as a formal occasion. At the very least, horses should be bathed and riders should have clean, neat clothing. There are riders who haven't been able to afford all of the accoutrements to a horse show outfit yet (one would hope that the reason is because they have used all available funds to provide their horses with excellent care and nutrition...) in which case there is a validity to not having tall boots and a show coat. That being said, it doesn't cost anything to clean up what you do have. If you don't know how to braid, get a friend to help you. Or at least, comb your horse's mane with some water to get it to lay flat. If you don't have clippers, use some scissors to tidy up your horse's bridle path and fetlocks. *warning - Do NOT use scissors to "even up" your horse's mane. Either pull it or leave it alone. A bob might have been cute on Dorothy Hamill, but it is not going to enhance your horse's features. Now, anyone under the age of thirty is saying "Who the heck is Dorothy Hamill?" I've got to pick up some more current references...
It is disrespectful to your judge, your horse and your fellow competitors to attend a show with a dirty, unkempt horse, shirt tail flapping in the breeze, crusty boots, and tack that hasn't seen saddle soap since it left the tack shop. Competing in a horse show with a disheveled appearance says to everyone, I don't really care.
I have judged horse shows in which riders enter their horses in Showmanship classes, which are judged on grooming and presentation of yourself and your horse, that looked like they just rolled down a hill. That tells me that A) This rider does not have the education to understand what the class is judged on. Or B) If the rider does have that education, she couldn't be bothered to prepare properly. The basic criteria for the class is grooming. If you can't even meet that, why have you wasted my time with entering the class? If you aren't sure of what any class you enter will be judged on, look it up or ask someone. If you know and you don't care, shame on you. Every time you present your horse in public, that horse should look like somebody really cares about it. Poor grooming exudes an air of neglect. I'm not a big fan of clipped whiskers, fake tails, face highlighter and some other extremes, but bathing, again, is wallet friendly and necessary. If you don't care enough about your horse to groom it properly, why should the judge reward you for that by giving you a ribbon?
Not only is lack of grooming disrespectful, it is distracting. The whole idea behind the show attire and braiding of horses, is to present a uniform appearance of all competitors so that only the skill and talent are evident. When a rider enters the ring with a turquoise saddle pad, dirty half chaps, and a tack that looks like it was put on by a committee, it draws attention. And not in a good way. It draws attention AWAY from your horse's movement and your equitation. That being said, fancy tack and a gleaming horse will never make up for bad riding, but it could give you an edge in the event that the judge can't decide whether to give you 4th or 5th place.
A schooling horse show is a dress-rehearsal for a recognized show. Even if you never plan to attend a recognized show, the occasion should still be regarded as such. Let's try to give it an analogy... If an acquaintance of yours was throwing a fancy dress party, would you attend in the same clothes that you wear to clean stalls? You would still be the same person, with the same personality that endears you enough to the host to be given an invitation but your appearance would give the impression that you are apathetic to the situation. You may find yourself being left off the next invitation list.
Of course, the most important thing at any show, is that you and your horse are healthy, sound, capable and fit to do the job. Good grooming and proper turnout should be the icing on the cake. I thought that was another useful analogy until I realized that there is a whole website (Cake Wrecks) dedicated to professionally decorated cakes that have gone terribly wrong. It's a fun website, you should check it out. After you've given your horse a bath.