California’s Transitional Kindergarten (TK) program provides an additional year of schooling within the K–12 system that aims to prepare children for kindergarten. Launched a decade ago with limited eligibility, the program will be expanded to all four-year-olds by 2025–26. Little is known about TK’s longer-term impact—especially among multilingual students and students with disabilities, who might benefit from early identification. Taking stock of TK’s impact so far can help the state expand it successfully.

This brief provides an overview of California's existing network of preschool centers and the potential impact of Proposition 82, which would provide funding for half-day preschool programs for 70% of the state's four-year-olds. PACE, an independent research center, aims to clarify evidence informing education policy options. A 2005 PACE review focused on enrollment patterns and policy options for improving access and quality of local preschools.