You have gotten some great advice but here is more because we were in the exact situation twice at Montessori! And resolved it twice...
So in her old montessori (before we moved across the country - we moved just after her 4th bday):
They did not realize she could read and at her midterm eval (just after she turned 3) they said "She has learned the following letter sounds: (then listed like 14 letters)". They said other crazy way off things about her math too. DH and I were so shocked we wrote a response to the evail and came in to discuss it a week later. By the end of the year they were accelerating her so much that DD was having a blast and I was wondering if they were moving even too fast. She was reading to the class a few times a week, ect. I think at one point they stopped the phonics books.
Her new school:
We did't want to "just wait and see" because we knew that actually didn't work. So we went in telling them she is level "J" reading and math, ect. We also had the old school write a letter. The new school evaluated her for two weeks and, were in agreement with the old school, but actually found out how behind she was in fine motor, only exacerbated by the fact that she was ahead academically. She had a hard time sitting (very weak core) in addition to very poor fine motor. This was delaying her in other areas because she was unable to write her numbers for math, write stories that she wanted to write, ect.
SO... there may be a secondary problem in addition to not wanting to complete the book. Like fine motor. At least worth looking into.
Our old school was VERY formulaic, you HAD to finish one book before going to the next, ect. The new school is very professional, and a whole different situation. They don't make you bother with one thing if they already know it. BUT they check to make sure you know every aspect of one thing before moving them along. For example, they have her in level E for reading (obviously way lower level than level J) but that is the level they are working with her so that she can re-tell stories, reading comprehension, ect. They said she can decode a much higher level than J even but comprehension is so important that she needs to be on E now. I do think they are right. She reads whatever she wants at home (usually Fancy Nancy). They said she read the history of Mona Lisa today at school (but likely she couldn't retell those facts, ect, for example). I do think comprehension and fine motor are important so I am glad they pin-pointed both. They suggested OT today for her core and fine motor. We have only been at this new school since January!!!
