Summary:
ZIP code 99003 has one high school, Riverside High School, serving grades 9–12 in the Chattaroy area near Deer Park and Milan. The school enrolls 432 students and is part of the Riverside School District, which ranks 62nd out of 238 Washington districts and has a four-star rating.
Riverside High School has several notable strengths. Its 2024–2025 graduation rate was 95.1%, nearly matching the district’s 95.6% and substantially exceeding Washington’s 82.6%. Academic performance was especially strong in English Language Arts and science. In 2025–2026, 67.39% of students were proficient in ELA, compared with 50.93% in the district and 52.81% statewide. Science proficiency was 55.26%, above both the district’s 48.56% and the state’s 50.95%. The school’s statewide position also improved, moving from the 54th percentile in 2023–2024 to the 69th percentile in 2025–2026.
Mathematics is the most important area for improvement. Only 34.09% of students were proficient in math in 2025–2026, below the district’s 44.00% and the state’s 43.11%; results were similarly low the previous year. ELA declined slightly year over year, while science improved by 2.68 percentage points. With a student-teacher ratio of 18.4 to 1, enrollment of 432, and nearly half of students eligible for free or reduced-price lunch, the school appears to offer a moderately sized setting with a range of student needs. Overall, families can expect strong graduation, ELA, and science outcomes, while math achievement remains the clearest academic concern.
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