I would ignore the teacher's email for now, (but do hold her to the 'end of the month' promise for bigger books)
and focus on the Principle, who has the power to move your child out of that room - full or part time.

It really isn't the classroom teacher's 'fault' that your child isn't in a place to benifit from what has always worked in the past. Every bit of training and experience is telling the teacher that their methods are 'right.'

Good luck,
Grinity

Coaching available, at SchoolSuccessSolutions.com