Cathy,
The book (or other icebreaker) idea is a fifty/fifty shot. If the teacher is like the public school teacher who assessed my daughter, then yes, she will probably imply that your son has memorized it. If she is has an open mind, like the assistant principle who assessed my son, she will congratulate him on how well he reads, then find a book of equivalent difficulty and ask in a friendly way if he could read some of it to her as well.
Like acs mentioned, you will learn a lot about the teacher by how she handles the assessment. By bringing a book, or other object of interest which demonstrates ability, you give that tester every opportunity to find your child�s range.
Diana
