Since we're all saying what we'd do, I'd get a new piano teacher.
DD5 started violin when she was 4 and liked it. I specifically told the teacher I was willing to pay for private because I DID NOT want her in Suzuki. No offense to all the fine suzuki children out there, DD5 doesn't have the right personality.
Fast forward to November. She has had DD play the same song over and over for 3 months. I send an e-mail because dd is getting frustrated and she responds that she knows what she is doing and basically she thought I was "projecting my feelings of inadequacy onto my child by trying to push her ahead."
Well, I won't go into details here, but I straightened her out pretty quickly. She didn't get that DD has a fine motor delay and would never "perfect" the piece to teacher's specifications at this point. It ended well and teacher started teaching DD to read music, which she is enjoying and likes to play off the music sheet, not from memory. Teacher was blown away at DD's ability to quickly pick up music reading.
I'm sorry but your teacher is very ignorant in terms of understanding cognitive abilities. Maybe there is a better teacher out there for you son.
Incog