Los Osos High
Rancho Cucamonga, CA · High School · Grades 9-12
Los Osos High is a high school in Rancho Cucamonga, CA with 2,837 students enrolled and a 58% proficiency rate. Part of Chaffey Joint Union High. NCES data from the U.S. Department of Education.
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About This School
Los Osos High is a high school located in Rancho Cucamonga, California. The school serves 2,837 students in grades 9-12. The student-to-teacher ratio is 24.9:1.
According to EDFacts assessment data, 58% of students meet grade-level proficiency standards in combined math and reading. The school reports a 86% graduation rate.
29% of students qualify for free or reduced-price lunch.
Los Osos High is part of the Chaffey Joint Union High in California.
How This School Compares
Los Osos High has 2,837 students enrolled, making it larger than the average school in Chaffey Joint Union High (2,096 students). Its 58% proficiency rate is 16 percentage points above the district average of 43%. Compared to the California state average of 45%, the school performs 13 points higher. The 24.9:1 student-teacher ratio is above the national average of 16:1.
Frequently Asked Questions
Los Osos High has 2,837 students enrolled in grades 9-12. The student-to-teacher ratio is 24.9:1.
According to EDFacts data, 58% of students at Los Osos High meet grade-level proficiency standards in combined math and reading assessments.
Los Osos High has a 86% graduation rate, measuring the percentage of students who graduate within four years.
Los Osos High is part of the Chaffey Joint Union High in Rancho Cucamonga, California. You can view all schools in this district on the district page.
All data on this page comes from the National Center for Education Statistics (NCES) Common Core of Data and EDFacts assessment results. These are official federal datasets published by the U.S. Department of Education.
School profiles are built from NCES directory data and EDFacts assessment results. Proficiency rates reflect combined math and reading performance. Graduation rates are reported for high schools with available data.
The this entity record above pulls directly from NCES Common Core of Data and EDFacts. What follows is the per-entity context — how this entity sits in the broader U.S. K-12 school outcomes and enrollment distribution and which underlying factors drive the headline numbers.
The methodology behind every numeric value on this page is publicly documented on the NCES Common Core of Data and EDFacts portal and described in detail on this site’s methodology page. Refresh cadence varies by underlying series; the page surfaces the as-of date for each number so readers can trace any figure back to the source release.
Practical use of this page is in combination with the comparison and ranking pages elsewhere on the site, which surface the same data for this entity’s peers within U.S. public schools and districts. A single-entity reading without peer context can be misleading when an entity is an outlier on one axis but typical on another.
Source: NCES Common Core of Data, 2026.