Most Montessori schools have kids using manipulatives from 18 months to build the muscles in their hands specifically for writing so I'm not suprised that his classmates are writing a great deal. However, I would be very surprised if this were such an essential part of his classroom work that it couldn't be ammended to suit his development level.

Have you discussed it with the teacher? Perhaps, he can do 50% and she'll transcribe the other half for him or be willing to make some other type of comprimise to eliminate the self-doubt and stress.

Mom to DYS-DS6 & DS3