Well, I can give someone a book but I can't make them embrace any of the advice inside, it's true. About all I can think of is if one were to work with the same horse and get much better results, very rare unless you are a pro trainer hired to do the job.
Actually, this could be fun. I've done some time in WP and reining barns, but it's been a while. Maybe someone with more experience would volunteer to play the role of bad WP/rollkur dressage/whatever trainer, and we can all practice. Could be fun?
Well I know my training paradigm is a lot differently than the one I was "raised with".
I come from a background of different tack/bits being the answer and drugging being a go to when that fails, and the general though of "when it goes wrong, it is the horse's fault!".
What change ME was getting away from any trainer/showing for bit and having three goofy morgans to start.
I do have a boarder whose mindset I want to change though. I really really like her as a person, and respect her as a rider, but as a "trainer" (not a pro, but trains her own) she seems adept at ruining work ethics. She isn't abusive, but pushes her horses hard and her idea of praise is just to say "good" and to try again (vs giving the horse a short break or moving on to something easier/fun). This has resulted in her horses ALL developing the habit of kicking out at her leg, rearing (small rears), some mild bolting, and general nervousness when ridden. her current horse is younger, and this training style is making him dangerous for me to lead out as well. (over reacts when he spooks, like he is afraid I will get after him for looking at something). Kicking out at her leg is also getting dangerous to others. When my students have ridden these same horses they find them to be very dead to the aids, but otherwise pleasant, and definately safe.
I wish I could find a way to get her to slow it down and be softer so her horse had a chance to listen to lighter aids, but she seems to soften/ease up for clinics, and then go right back to her way after a few days.
Good luck. Let me know when you change that persons mind. I tried, it didn't work, and I gave up because the person was too embarrassing to be around, to pig headed to listen to anyone, and too obnoxious to take advice. She continues to ruin horses, and the horses continue to rear and be bad because of her. She will never learn. She has been riding for over 20 years and hasn't changed yet, she has been peeled off the ground and she blames it on the bad horse.
OP, if I read it right you are the BO? Then as a BO, you do have one way to do it, which is to drag her into the office and give her a speech using the phrases you had in your second post back there. It might, might, penetrate if you tell her she has 90 days to shape up or move out. Tell her she's a great boarder, you love her horses and you like what you see after a clinic but you don't like the fact that her horses as a group develop the same sorts of negative behaviors and the only common factor is her method of riding/training.
You do have the right as a BO to remove her from association with your barn name.
Will that change her method? Only if you can also offer to assist her in replacing her negative methods with something more positive, I mean face it she's developed this training style and probably doesn't think anything about it, or thinks that she's been cursed with the only group of horses that kick out and evade upwards. If she gets better after clinics then she may just need some eyes on the ground to tell her when she is backsliding, the fact that she does get better afte clinics is a good sign to me, it says she's willing to change, but she is reverting to what she knows after a period of time.
Of course she could also think you're a controlling beeyotch trying to blackmail her into paying for lessons too. I hope not.
Ride with her yourself on a young horse. Do a "good boy" and release (whatever you do, move onto another task, walk or stand, whatever). Do it very obviously every time you ride with her. That may be the only way she changes is if she follows your lead and sees the benefits. Otherwise... probably a lost cause, with horses especially people are very set in their ways.