San Mateo County's public school classrooms are getting a little quieter. Between the 2021–22 and 2025–26 census-day counts, public school enrollment fell by roughly 3,556 students, about 4 percent of the countywide total. The slide is uneven: 16 of the county's 23 school districts lost students while seven districts grew, and county charter programs also shed hundreds of pupils. That mix is about to shape budget choices and program offerings as districts prepare for the fall.
Those figures come from the state's official Census Day files, the single-day fall snapshot the state uses to report TK–12 enrollment, according to the California Department of Education. A local column in the San Mateo Daily Journal highlighted the trend this week for county readers. The CDE publishes district and school files so districts, researchers and the public can check the counts for themselves.
2025–26 District Tallies
District rolls for 2025–26 still feature several big players. San Mateo-Foster City, Sequoia Union and San Mateo Union High are all hovering near the 9,000-student mark, while South San Francisco Unified comes in at roughly 7,600 students, according to public profiles. County and district summaries collected by data portals including Ed-Data make the 2025–26 snapshot easy to scan. The overall four percent county drop reflects a mix of shrinking high school systems and a few elementary districts that are still growing.
Biggest Declines And Where Growth Showed Up
On a four-year comparison, some of the largest raw enrollment losses hit Sequoia Union, down about 711 students, and San Mateo-Foster City, down roughly 649. Other sizeable drops landed at San Mateo Union High, Redwood City Elementary and Jefferson Union High. Percentage-wise, Cabrillo Unified, Pacifica Elementary and Ravenswood posted some of the steepest proportional declines, and county charter schools together lost about 813 pupils between 2021–22 and 2025–26.
Not everyone is shrinking, though. A handful of elementary districts moved against the tide. San Carlos recorded the largest gain, up roughly 339 pupils, about 11 percent, according to a breakdown reported by the San Mateo Daily Journal.
Budget Pressure And What Districts Can Do
Fewer students do not just mean emptier playgrounds. Falling headcounts can quickly translate into less state funding because many apportionments and grants are tied to attendance and enrollment formulas. Independent analysis from the Legislative Analyst's Office details how enrollment and average-daily-attendance figures shape state apportionments and affect district cash flow.
Locally, the San Mateo County Office of Education maintains data dashboards and research so districts can track trends, consider staffing adjustments and plan enrollment-management strategies as the fall budget season approaches. County officials have also pointed to early-learning investments as one lever to support longer-term enrollment stability.
District boards now face a near-term ledger test. With fewer students and less predictable revenue, leaders will have to weigh program consolidation, targeted recruitment and other moves to protect core services. Observers will be watching updated CDE files and district budget statements to see which specific actions follow.
