Summary:
ZIP code 91765 has one listed high school, Diamond Bar High, serving grades 9–12 and enrolling 2,563 students; the available test results cover 2024–2025 and 2025–2026. Since it is the only school listed, there is no local school-to-school comparison. The most important finding is that in 2025–2026 Diamond Bar’s proficiency rates were above California’s in all three subjects: by 29 percentage points in English language arts (ELA), 29 in math, and 22 in science.
Diamond Bar High is the area’s sole reported school, rather than a local leader or trailer. Its 2025–2026 proficiency was 78% in ELA, 68% in math, and 58% in science. Compared with Walnut Valley Unified, it was 3 points higher in ELA but 5 points lower in math and 6 lower in science. Other outcomes compare favorably with the state: graduation was 96%, 9 points above the state rate, and dropout was 2%, 6 points below the state. Chronic absenteeism was 7%, 11 points below the state, but 2 points above the district.
Recent achievement changes were mixed: from 2024–2025 to 2025–2026, ELA proficiency rose 2 points, math fell 1 point, and science rose 4 points. The school’s average gap above the state across the three subjects remained about 27 points, so the overall state-relative position changed little. SchoolDigger gave Diamond Bar High 5 stars and a 95th-percentile ranking, placing it 102nd of 2,137 schools in 2025–2026; its ranks were 84th and 98th in the prior two reported years. The listed student–teacher ratio was 26 in 2024–2025, and 23% of students were reported as free/reduced lunch eligible that year. With only one school listed, these figures cannot show local variation or identify exceptions among nearby schools.
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