Los Osos High School Home

About Us

The Chaffey Joint Union High School District serves the communities of Ontario, Montclair, Rancho Cucamonga, and portions of Fontana, Upland, Chino, and Mount Baldy. With over 25,000 students, the District is the fourth largest high school district in California. It has eight comprehensive high schools, a continuation high school, an online high school, a community day school, an adult school, and alternative programs. The District offers a wide variety of instructional options that provide a quality education for each student, every day. The District's well-prepared, dedicated, and highly qualified teachers and support personnel are second to none.
The Chaffey Joint Union High School District Board of Trustees are steadfast in the belief that "Nothing is more important than student learning and their achievement."
Our daily purpose encompasses our commitment:
"To provide student learning, and ultimately their achievement, of the prescribed curriculum that takes place in the classroom under the direction of the teacher." The Chaffey District supports this daily act. We realize that our efforts uniquely influence the future of our community and of this nation, and we are passionate about doing whatever it takes to prepare students to be successful and contributing citizens of the 21st century.
The Chaffey District has provided a quality education for high school students in the area since 1911. As the District continues to grow and progress, we are poised to meet the challenge of providing the finest quality education possible for every student. 
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All CJUHSD students will graduate ready for college and careers.

Recent News

Summer School

View the 2023 Summer School calendar and bell schedule.

Upcoming Events

School Facts

  • 78% of Los Osos High School graduates meet the University of California and California State University A-G admissions requirements, making it a leader in San Bernardino County.
  • 98% of freshmen at Los Osos High School complete their first year of high school on track to graduate.
  • The CJUHSD has been named a Top Workplace by the Press-Enterprise and Inland News Group.
  • 2500 Advanced Placement exams are administered to students at Los Osos High School annually.

Principal's Message

Mr. Cypher
Welcome back and welcome to the start of second semester! I hope you had a restful Winter Break and that you are ready to finish the year strong!    
It has always been my practice as I begin the new year to reflect on my previous years goals and to realign them for the new year, a simple New Year’s tradition!  I challenge you to do the same and take some time to reflect on this past year/semester and set some academic and personal goals.  This is a great opportunity to reset and start anew; but to really put in some practices in place that will become habits! 
To help assist in creating those habits here some resources that are available to help keep you on track to meet those academic goals: 
After school tutoring  
Paper Tutoring Services  
4G Saturday School  
Counselors and Teachers  
As a reminder, school is not in session on the following dates:  
January 16th  – MLK JR. Day  
February 13th – Lincoln’s Day  
February 20th – Presidents Day  
March 27st – 31st – Spring Break   
Stay strong Grizzlies remember to continue to work hard, inspire others, lead with integrity and dream big! 
Claws Up!   
Eric Cypher 
Los Osos High School