California Study Links Early Preschool and Transitional Kindergarten to Major Academic Gains
A comprehensive study on California’s multibillion-dollar investment in early childhood education shows that state-backed preschool and transitional kindergarten programs deliver measurable academic advantages years down the line. Commissioned by Stanford University and conducted by UC Berkeley researchers, the evaluation found that children enrolled in California’s early transitional kindergarten programs scored 11 months ahead in reading and eight months ahead in math by the third and fourth grades when compared to peers born in the same months prior to the program’s inception.
The legislative foundation for these gains dates back to a 2010 law that took effect in 2012. That legislation established transitional kindergarten—commonly known as TK—allowing a limited group of children with fall birthdays to complete a full academic year before standard kindergarten. The law simultaneously adjusted eligibility rules for state-funded preschool, expanding enrollment opportunities for children starting at age three. Today, California is in its second year of a full statewide rollout offering free TK to all four-year-olds. Data from 2025 indicates that just over half of eligible children are currently enrolled in the grade level, trailing state projections. Nonetheless, state funding remains substantial, with approximately $4.1 billion budgeted for TK during the 2025-26 school year alongside an additional $2.8 billion allocated for state preschool programs.
Rucker Johnson, a public policy professor at UC Berkeley and co-author of the study, emphasized that the impact of early education investments reaches far beyond elementary school testing metrics. He described the initiative as an opportunity to support children whose potential might otherwise be constrained by external economic challenges. “We call it finding the lost Einsteins,” Johnson said. “There are people who have the capacity, but without the investment, they don’t realize that potential.”
For decades, researchers have documented a persistent achievement gap between children from wealthier families and their lower-income peers. Austin Land, a Berkeley researcher and co-author of the study, noted that a child’s family income at the time of kindergarten entry often dictates their trajectory in standardized testing rankings. The new study, published by the nonprofit Learning Policy Institute and funded by several major foundations including the William T. Grant Foundation, Heising-Simons Foundation, and Ballmer Group, indicates that early education can help bridge that divide. Researchers tracked 1.6 million children who entered kindergarten between 2011 and 2014, contrasting the later reading and math outcomes of students who accessed TK with those who did not.
The data showed that low-income children with English-speaking parents experienced roughly seven additional months of learning in third-grade reading and math from TK alone. While wealthier children also benefited, their gains were smaller, likely because they already possessed access to private preschools and alternate educational resources. Furthermore, low-income children from homes where parents spoke a language other than English who attended both preschool and TK demonstrated fourth-grade math gains roughly five times larger, and reading gains three times larger, than estimated benefits for students who bypassed state preschool entirely.
Classroom educators report seeing these foundational advantages firsthand. Marylou Escobar, a kindergarten teacher with 41 years of experience at John Muir Elementary in Glendale, noted a distinct difference between students who attended TK and those who came from varied backgrounds. Among her 20 students, seven completed transitional kindergarten. Escobar observed that TK alumni already understand how to sit on the classroom rug, listen attentively, handle a pencil, and work independently, allowing instruction in letters and syllables to begin immediately. In contrast, children without that background often require initial instruction in basic classroom orientation, such as maintaining attention spans for five to 10 minutes. “They are ready to learn, whereas the other children are preparing themselves to learn,” Escobar said.
Anna Markowitz, an associate professor of education at UCLA who was independent of the research team, characterized the findings as striking within a field where academic benefits from preschool have occasionally been observed to fade over time. Markowitz noted that even a single month of additional learning would typically excite researchers, though she cautioned that early education is not a universal solution. Instead, she described the study as a clear proof of concept demonstrating that TK and preschool contribute to sustained benefits when integrated with the broader educational environment.
Johnson characterized the results as a multiplier effect, suggesting that each successive educational investment—from preschool to TK and elevated school spending—compounds the value of the next stage. Looking ahead, researchers hope to follow these student cohorts into high school and college to determine whether early academic advantages translate into improved graduation rates and enhanced college readiness.
Markowitz pointed out that foundational skills often begin with basic milestones, such as a preschooler learning to put on a jacket. The process requires multiple steps, physical coordination, and perseverance through initial frustration. Mastering these early competencies enables children to tackle more complex challenges later in life, including reading comprehension and advanced mathematics. “Learning to pay attention, learning to feel excited about trying something new or challenging—that stuff carried forward means everything,” Markowitz said.
