A mentoring service should not be needed if a consistent standard is there in the first place, no?
I always thought the CFI or equivalent was the ultimate mentor of any given organisation, and that's for both students and instructors.
It might even mean in some cases re-directing students to a better instructor with higher standards.
The "standard" is not always the root cause of a student's learning difficulty. Sometimes it is purely an incompatibility of personality and/or teaching/learning styles and nothing to do with standards that causes individuals not to progress at the "expected" rate.
Perhaps you meant 'alternative' instructor Aeromentor?
We're all human and we all work differently. A good quality in flight instructors (no matter what level they are at) is the ability to perceive these differences in students, and an 'adaptability' to suit the individual's needs.
I even see this in cyclic sims as I'm sure many others do here. As trainees, we repond/perform better with certain Check/Training Captains than others.