In a class with such a wide age range of children, won't my five-year-old spend the year taking care of younger children instead of doing his or her own work?
The five year olds in Montessori classes often help the younger children with their work, actually teaching lessons or correcting errors.
Anyone who has ever had to teach a skill to someone else may recall that the very process of explaining a new concept or helping someone practice a new skill leads the teacher to learn as much, if not more, than the pupil. This is supported by research. When one child tutors another, the tutor normally learns more from the experience than the person being tutored. Experiences that facilitate development of independence and autonomy are often very limited in traditional schools.