ARS 15-821C is the source of information for kindergarten entry age. It states that children must be five (5) years of age before September 1 to enter kindergarten. That means that a child must turn five on or before August 31, not on September 1. Kindergarten is not required in the state of Arizona.
While the deadline for admission to kindergarten is 5 years old by September 1, Arizona Revised Statutes (A.R.S.) § 15-821C gives districts the right to choose to allow students into a kindergarten program if they were born no later than January 1 and if they feel that it is in the best interest of the child. Many districts hold hard and fast to the September 1 deadline; some districts evaluate each child if they are an early-entry candidate and make a case-by-case decision, while other districts allow all children who turn 5 on or before December 31 to enter kindergarten.
Schools reserve the right to test students for entrance directly into first grade even if they meet the age 6 requirements for admission into first grade, and may choose to place them in a kindergarten program at that time if they do not meet the kindergarten standards.