Naptime (or rest time) is an important part of the day. It allows children a time to recharge and to process the experiences of the day. This restful period (from 12:30 to 2:30 PM) also prevents the child from becoming overly worn-out. When a child is exhausted they can become moody and difficult even (or especially) at nighttime when bedtime comes around.
The naptime process is also a lesson in practical life. The children begin by preparing their sleeping area by placing their crib-sized, fitted sheet and blanket (both labeled and brought from home on the first day of school) on their school-provided sleeping mat. They must rest quietly on the mat for one hour and can fall asleep if they want to.
The children again demonstrate the qualities of a normalized child: a love of work (choosing whether to fall asleep or to just rest), concentration on work (focusing on the quiet nature of rest), self-discipline (following through with the rest time process), and sociability (respecting the other children who are also resting or sleeping.)
Children are never forced to sleep and if they done resting after an hour they are free to select a quiet activity as to not disturb the other children who are still resting or sleeping.
It goes without saying, that in the case of little children such a long school-day should be interrupted by at least an hour's rest in bed.
Maria Montessori