Most of us worry. :-)
aeh has, as usual, excellent advice.
I am sharing our experience, because while it's a sample of one, there are some similarities which may be helpful. We have a child who was also in Montessori (an excellent one) through age 5. He had scores in the range of your daughter (although he was not tested until after first grade). Knowing what we know now, skipping first grade would have been a blessing and avoided the disaster that was first grade. He did not have it in him to tolerate curriculum that he had covered previously. This led to all kinds of issues that year (and to some extent, beyond).
That said, a great deal depends upon the public school's flexibility and willingness to look at the individual child's needs. I take it continuing in Montessori is not an option?
