As much as your idea makes sense to those of us in the trenches, I'm afraid the non-trusting "powers that be" above us would have this type of reaction:
"The guiding teacher may not know who's exam is being discussed, but they would know that it is one of their students which could bias their response in favor of a higher score."
It's such a lousy feeling.....not being treated as a professional....not being trusted.....all because of a few "bad apples". It's somewhat the same as why we all have to remove our shoes at an airport....all because of one human being. Ridiculous!
I wish you luck in your search for a solution. I think regional scoring is your best option.
Mathematics Department Chair JFK High School 305 Cayuga Creek Road Cheektowaga, NY 14227 (716)897-7800 ext. 1120
"We the willing, are doing the impossible for the ungrateful. We have done so much for so long, with so little, we are now qualified to do anything with nothing."