Transitional Kindergarten More Developmentally Appropriate When Classrooms Are Not Combined, AIR Study Finds

San Mateo, Calif. – With transitional kindergarten now fully implemented in California, the American Institutes for Research (AIR) has published a new report examining program features, including teacher qualifications, classroom structure and instructional content. Three-quarters of transitional kindergarten classrooms are standalone classrooms serving only transitional kindergarten students; 24 percent are combined with traditional kindergarten.

Transitional kindergarten grew out of California’s Kindergarten Readiness Act, passed in 2010. Historically, the state required children to be 5 by Dec. 2 to enroll in kindergarten. When the new law moved the cutoff to Sept. 1, transitional kindergarten was created for children who turned 5 between Sept. 1 and Dec. 2. The program was phased in over three school years, ending in 2014-2015. 

The study, conducted during the final year of the rollout, is based on teacher surveys and/or observations of 240 classrooms representative of transitional kindergarten in California. Notable findings include:

Transitional kindergarten class sizes vary, but the average is 20 children—well below the state-imposed maximum of 33 per classroom. Classrooms studied had 8 to 30 students.

All transitional kindergarten teachers have a bachelor’s degree; 96 percent have taught kindergarten. Half of program teachers also reported holding a master’s degree. A quarter have experience teaching preschool.

Most program classrooms are full day and standalone. Nearly two-thirds of transitional kindergarten classrooms are full-day programs, offering about six hours of instruction. Three-quarters of classrooms are standalone, enrolling only transitional kindergarten students as opposed to combining them with traditional kindergarten students. Some districts have combination classrooms because they have few students who qualify for transitional kindergarten.  

Standalone classrooms focus on a variety of content areas. Combination classroom teachers spend 67 percent of instructional time on literacy and math. Standalone classroom teachers spend 39 percent of their time on those subjects and devote relatively more time to social and emotional learning, music, art and social studies. Both types of classrooms spend the largest share of their daily instructional time on reading.

Transitional kindergarten teachers overall showed moderately high-quality interactions in terms of emotional support, or fostering warm, supportive relationships among teachers and students. This attribute is associated with growth in reading and math achievement. As for instructional support, which predicts students’ cognitive outcomes, quality was in the low to low-mid range, which is consistent with findings from national studies on early learning and kindergarten.

Overall, transitional kindergarten students spend about a third of their time being taught in a group setting, also known as whole-group instruction. In standalone classrooms, students spend most of their day in the activities of their choosing, which is considered developmentally appropriate for their age.

This report is the latest from a multiyear study of transitional kindergarten in California. To read past reports, including one that looks at transitional kindergarten’s initial impact, visit the study’s website.

About AIR
Established in 1946, with headquarters in Washington, D.C., the American Institutes for Research (AIR) is a nonpartisan, not-for-profit organization that conducts behavioral and social science research and delivers technical assistance both domestically and internationally in the areas of health, education, and workforce productivity. For more information, visit


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