River Delta Joint Unified

The 10 schools in River Delta Joint Unified include four elementary schools, two middle schools, three high schools—including a continuation school—and one alternative school, serving students from elementary through high-school grades. In 2025–26, the average school result was below the state in all three tested subjects: 41% in ELA versus 49% statewide, 20% in mathematics versus 38%, and 26% in science versus 36%. Results also varied sharply from school to school, so a district-wide picture can hide important differences; the most important finding is that no single result describes performance across these schools.

Isleton Elementary is the clearest standout in math and science, with 53% proficient in math and 60% in science—15 and 24 percentage points above the state, respectively—and a SchoolDigger ranking at the 73rd percentile. Delta High leads in ELA at 56% and ranks at the 50th percentile on SchoolDigger. At the other end, Clarksburg Middle has the lowest All Grades ELA result, 25%, and the lowest listed current SchoolDigger ranking, at the 9th percentile. Rio Vista High has the lowest math result, 7%, which is 31 percentage points below the state; Walnut Grove Elementary has the lowest reported science result, 7%.

From 2024–25 to 2025–26, the average school result improved by 4 percentage points in ELA and 4 points in science, while the math average fell by 3 points; the gap with the state narrowed in ELA and science but widened by 4 points in math. School context also differs: 2024–25 free/reduced lunch eligible (FRL) shares ranged from 67% at River Delta High/Elementary (Alternative) to 94% at Bates Elementary, while student-teacher ratios ranged from 8.8 at Mokelumne High (Continuation) to 23.5 at Isleton. Attendance is another notable difference: chronic absenteeism was 7.5% at Isleton and 25.2% at Rio Vista, while Mokelumne reported 100% and has no supplied proficiency results. Small enrollment and unavailable results make some schools difficult to compare directly.