Unlocking the Potential of Transitional Kindergarten Requires Better Data on Early Education

Examining two high-quality studies of TK conducted before the UTK expansion and new guidelines that took effect in 2022–23 helps illustrate the capabilities of the current data system as well as how the data system should be expanded to make it more useful for understanding TK program quality. One study was based on substantial original data collection; the other relied solely on administrative data. Both used a regression discontinuity design—a research design that offers the strongest nonexperimental methodology for estimating program effectiveness.

The first study (Manship et al., 2017)examined students enrolled in TK during the 2013–14 and 2014–15 school years who turned five between October 2 and December 2. The study collected data on the features of TK classes (full day versus half day, as well as TK/kindergarten blends or solely TK) and instructional quality; the authors also collected original data on the prior educational experiences of students in the comparison group who had not attended TK. The research team followed students into kindergarten, administering assessments in literacy, mathematics, and SEL skills at the beginning and end of kindergarten to both former TK students and their peers who did not attend TK (the comparison group). The results showed the initial benefits of TK, but uncovered that students who had not attended TK caught up with the TK students on most measures. The authors suggest that the fade-out of the TK effect may be explained by a finding in other studies: teachers prioritize students who enter kindergarten behind their peers and, in the process, do not provide the types of vertically aligned experiences that research suggests are critical for promoting student learning. In short, these findings are provocative for thinking about how to structure TK programs and—crucially—to improve the alignment of TK with K–12 so that students sustain the benefits of the TK experience.

While the 2017 study did not include any longer-term measures, a more recent study did: Lafortune and Hill (2023) followed the same TK cohorts from TK through Grade 5 in five of the state’s largest districts, with a focus on the trajectories of dual language learners and students with disabilities. This study found some benefits resulting from TK: earlier identification of special education needs and of English learner status. There was also some evidence of improved SEL for TK participants, though not among multilingual learners. However, the study did not find significant positive impact of TK on third and fourth grade test scores in English or math—at least not relative to the study districts’ alternative preschool programs, which included California State Preschool Program (CSPP) and Head Start. These findings are consistent with prior research on PK programs, which often showed additional academic improvement fading in elementary school—even for programs that saw notable long-term improvements for their students in high school and beyond.

These studies were well designed and executed but both have limitations. Manship et al. (2017) provided more context on the TK setting and available alternatives (through original data collection) but told us little about whether impacts continued later in school—that is, beyond kindergarten. Conversely, Lafortune and Hill (2023) provided some longer-term context (through Grade 5) but lacked data on key features of implementation that drive TK quality, including class sizes, educator qualifications, full-day versus half-day schedules, and language modalities. Critically, the 2023 study had no way to assess students’ trajectories between the time they left TK and the end of their third grade year, so it is impossible to draw conclusions about the extent to which the lack of significant differences in third and fourth grade achievement between TK and non-TK students was due to (a) strong CSPP and Head Start programs in which comparison students were enrolled; (b) poor coherence in K–3 learning, such that initial gains from TK had faded by third grade; or (c) implementation of TK programs in ways that led to few long-term positive outcomes.

Both studies, moreover, were of cohorts prior to expansion and so provide no evidence about the efficacy of UTK, which includes policy changes designed to improve quality and consistency. As UTK expansion continues, policymakers and practitioners have little research to answer questions about how well current TK programs are serving student needs or what program features best promote kindergarten readiness—and longer-term academic and SEL improvements.

Additional research will need to be conducted to see if UTK is meeting its potential to improve students’ long-term outcomes. But for this research to uncover relevant and actionable policy insights, better and more comprehensive data will be necessary as well. The state should also require districts to track the data they need to improve the quality of their own TK programs and these programs’ coherence with K–3. Specifically, the state should do the following:

• Collect the basic features of each early childhood program—at a minimum, the state-funded TK and CSPP—including length of school day, class size, teacher credentials, staffing ratio, and program model (e.g., TK only, TK/K blended). Understanding the language learning environment experienced by the youngest dual language learners is also important, given that approximately 25 percent of TK students are English language learners. For students who did not participate in  state-funded programs, the state should require districts to collect and report basic information about students’ experiences before they enter kindergarten (e.g., Head Start, family/friend/neighbor care), which could be gathered as part of kindergarten enrollment.
• Require districts to administer and report a developmentally appropriate measure—such as the DRDP—to assess students’ academic and social-emotional skills as they enter kindergarten. While the issue of assessing younger learners is complicated, multiple developmentally appropriate measures exist that could provide a baseline measure of students’ skills when they enter the K–12 system. Having a universally required assessment at the beginning of kindergarten would support evaluation of the range of early childhood programs and, crucially, would provide districts with the type of data they should be using to support provision of vertically aligned learning opportunities for students.
• Recommend that districts locally select and administer assessments from kindergarten through second grade. Districts could use such assessments to examine whether their systems are sufficiently coherent from TK–3 to leverage the benefits of TK and make improvements in alignment if districts find that the initial benefits of high-quality early learning fade over time.

Collecting these data would allow districts and the state to identify effective TK program features and assess the coherence of learning opportunities provided from kindergarten into the primary grades. This data-driven approach is essential for both accountability and improvement, ensuring that the investment in UTK yields positive and lasting outcomes for students.