Best Length of Day at School for Preschoolers

My 4-year-old son now goes to preschool three days a week - 3 hours each session. Next year, I can either send him for the same amount of time or have him go for six hours, three days a week. How do I decide how many hours he should attend preschool? - An Issue of Time
Answer: There are absolutely no hard and fast rules about how many hours a child should spend at preschool. In making this decision, think about how your child is responding to preschool now. Does he enjoy it? Would he like to spend more time at school? Or is he finding preschool frustrating and would like to spend more time at home? It's also fair to consider whether you would like the child to continue having the additional time with you. There are decided advantages for young children having one-on-one contact with adults, as it encourages the development of speaking and vocabulary skills.
Before deciding to enroll your child in the longer program, be sure that he is developmentally ready to spend the additional time at school. Will six hours at preschool be too tiring for him?
Do keep in mind that young children change very quickly. If your son doesn't appear ready for more time at preschool now, ask if the program is sufficiently flexible that he could enter the longer program later.