AIR Study Finds California’s Transitional Kindergarten Gives All Students an Advantage for Kindergarten

Washington, D.C., June 28, 2017 (GLOBE NEWSWIRE) -- Students who attend California’s transitional kindergarten (TK) program enter kindergarten with stronger mathematics and literacy skills and are more engaged in their learning than students who did not attend TK, according to a new study released today by the American Institutes for Research (AIR). The program provides advantages for all students, with particular benefits for English learners and low-income students, and its benefits hold up regardless of variations in instructional practices or classroom structure. The study is based on the final report from AIR’s multi-year study of TK in California.

“Transitional kindergarten gives students an advantage of 3-6 months of learning in literacy and mathematics skills at kindergarten entry, which is quite notable, especially given that a large majority of the comparison students attended preschool themselves,” said Heather Quick, AIR managing researcher and study principal investigator. “These impacts did not vary by classroom characteristics, suggesting that the unique features of TK that set it apart from other prekindergarten programs—credentialed teachers, alignment with kindergarten, and inclusion of students from all income levels—may be driving the program’s positive results.”

TK, the first year of a two-year kindergarten program, was established by California’s Kindergarten Readiness Act, passed in 2010. Historically, the state required children to be five years old by December 2 to enroll in kindergarten. When the new law moved the cutoff to September 1, TK was created for children who turned five between September 1 and December 2. Using the TK age cutoff to compare children eligible for TK (those born within a 60-day window on or before December 2) with their non-eligible peers (those born in the same window after December 2), the report estimates the impact of TK on school readiness skills of more than 6,000 students across 20 school districts. This study design enables researchers to attribute differences in outcomes between TK students and non-TK students, though the generalizability of the results to students outside the narrow age range around the cutoff date may be limited. For example, we do not know if TK would be effective for students several months older or younger than those studied.

Notable findings include:

  • TK gives students an advantage at kindergarten entry on a range of literacy and mathematics skills, including letter and word identification, phonological awareness, expressive vocabulary, problem solving, and knowledge of mathematical symbols and concepts. Students who attended TK were also rated as more engaged by their teachers, compared to their peers. These advantages are notable given the large percentage (over 80%) of students in the comparison group who attended preschool while eligible students were enrolled in TK.
  • TK is effective for all groups of students who participated. It showed a particularly strong impact on language skills for English learners and mathematics skills for low-income students at kindergarten entry.
  • TK has no detectable impact on students’ executive function or incidence of problem behaviors at kindergarten entry.
  • Impacts of TK are smaller at the end of kindergarten, though TK students continue to have an advantage over non-TK students on letter and word identification skills. Overall, non-TK students appeared to catch up with their TK peers on most measures, although both TK and comparison students demonstrated growth at or above what would be expected for their age on several assessments. The impact of TK on the literacy and mathematics skills of low-income and Hispanic students also persisted through kindergarten.
  • There was little variation in the impact of TK by classroom or instructional characteristics. Standalone classrooms were not significantly different from TK/kindergarten combination classrooms in their impact; half-day and full-day classrooms showed similar effects; and differences in assessed quality of teacher-child interactions did not change the program’s impact. These findings suggest TK’s positive impact for students may be driven by the characteristics that TK programs have in common (and that make TK a unique approach to prekindergarten): credentialed teachers with bachelor’s degrees, close alignment with kindergarten, and inclusion of students from all income-levels.

Researchers in the San Mateo, California office of AIR have been studying the state’s TK program since 2011, with support from the Heising-Simons Foundation, the David and Lucile Packard Foundation, and First 5 California. The Impact of Transitional Kindergarten on California Students: Final Report from the Study of California’s Transitional Kindergarten Program is the final report from the multiyear study. Past reports, including one that examines TK’s impact on English learner students and the characteristics of TK classrooms, can be found on 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



A photo accompanying this announcement is available at


A photo accompanying this announcement is available at


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