There never will be.
Yet we as a society and even as teachers strive for perfection. The photos of Joseph Pilates spine to match that of our clients in less than a year when in reality for some it may take a lifetime. Perhaps a better idea would be to not judge and just acknowledge some circumstances (especially as teachers) are out of our control.
The athlete may get injured. People need to go away on vacation and may miss workouts. Sometimes what appears to be setbacks however is just forward progress in disguise. When in doubt the breath and the engagement of the core (our basic Pilates principles) are the foundation for all of good movement patterns.
For me personally, I find it more rewarding to teach a client with an injury or imperfection. I can see the progress more clearly. I can see the soul open up. I can see the changes unfold. The confidence build with the improved posture. Over time they realize they want to eat better and do more self care. They become a more happy complete person. That to me is where the reward lies.
May we all learn to be patient with the practice and enjoy each day as another opportunity to uncover a new layer. No matter if that is a layer in the system of Pilates or in ourselves.