Awesome chart from the Children's Defense Fund sums up the state of state-level policies on full-day kindergarten. Ten states and D.C. mandate* full-day K--all of them except for New Mexico located in the South. Accompanying state-specific fact sheets provide greater detail, including birthday cut-off for kindergarten entry, age of compulsory school attendance, state funding for kindergarten, kindergarten standards, and kindergarten entry assessment. Great resource for anyone interested in early childhood, PreK-3rd, or kindergarten policy.
Kudos to CDF for looking into this topic. Kindergarten often gets short shrift in public policy discussions, which tend to focus more on preschool/pre-k or the elementary grades. The recent state Early Learning Challenge Race to the Top competition, for example, focused on building state systems for "birth to 5"--but did nothing to address children's access to high-quality or full-day kindergarten. That's a mistake. Kindergarten is a critical year for children's development and learning--and all the more so as states move to implement Common Core standards. And providing a full-day is important not only to ensure children are able to master the concepts and content that Common Core is expecting, but to ensure schools have time to support this learning in a developmentally appropriate way that leaves plenty of room for play and exploration, which are essential at age 5. Even as we debate whether or not to expand public investments in pre-k, it's important to remember that not only is full day K far from universal--but some states don't require districts to offer kindergarten at all!
*Update: I realized the way I use "mandate" here is confusing--I meant that these states have laws requiring full-day K to be offered, not necessarily requiring students to attend full-day K. About half of these states make kindergarten mandatory for children.