Community High School District 155 includes four comprehensive high schools and one alternate education campus. Serving grades 9-12, each institution has full State of Illinois recognition and accreditation. All four District 155 high schools ranked in the top 10 percent of public high schools nationally by U.S. News & World Report in 2020, which identifies the superior education our students receive. All four high schools also earned a spot in the top 100 best high schools in Illinois for 2020. These recognitions are the results of our student-centered approach at each of our high schools. Newsweek named three high schools as top STEM high schools and Niche ranked D155 as the best school district in McHenry County.

Enrollment includes 5,973 students from Bull Valley, Burton's Bridge, Cary, Crystal Lake, Fox River Grove, Lake in the Hills, Lakewood, Oakwood Hills, Prairie Grove, and Ridgefield. The district covers 67.75 square miles and is located approximately 45 miles northwest of Chicago in McHenry and Lake counties.​

Beginning in 1884, a single public school, Union School, taught all Crystal Lake elementary and high school students. In 1907, the high school moved into its own building on the Union School grounds. Twelve years later, Community High School District 155 was established by a ballot measure in December of 1919. H.A. Dean served as the district's first superintendent. Crystal Lake Community High School opened at the current site of Crystal Lake Central High School on May 12, 1924. The school served students from Crystal Lake, Cary, Fox River Grove, and the surrounding areas, all of whom attended Crystal Lake Community High School until 1961, when Cary-Grove High School was opened. Crystal Lake South High School opened in 1978. At that time, Crystal Lake Community High School became Crystal Lake Central. A fourth high school, Prairie Ridge, opened in 1997. The district opened an alternative education campus, Haber Oaks Campus, in 2008​.

Students come to the high schools from several public elementary school districts including Crystal Lake District 47, Cary Community Consolidated School District 26, Fox River Grove School District 3, and Prairie Grove School District 46.

All District 155 juniors take the SAT which measures academic progress of current juniors and assesses college readiness. Previously, all juniors took the American College Test (ACT). The composite score for Community High School District 155 seniors graduating in 2019 was 528.9 in the English Language Arts portion and an average of 538.1 in the Math portion compared to a state average of 497.5 in ELA and 497 in Math. During the 2019-20 school year, a total of 2,801 Advanced Placement® exams were taken and 72 percent of students earned an honor score. Furthermore, 87 percent of the students in the class of 2020 continued their education beyond high school at 2- or 4-year colleges/universities or technical/vocational schools.

The district employs over 725 people including teachers, school counselors, social workers, school psychologists, school nurses, support staff, special education services personnel, and administrators. Approximately 83 percent hold master's degrees or higher.

District 155 is one of Illinois' most financially healthy school districts, having received the highest financial rating from the Illinois State Board of Education for each of the last 16 fiscal years. The Financial Recognition rating is based on fund balance to revenue ratio, expenditures to revenue ratio, days cash on hand, short-term borrowing, and long-term debt. For the fifth year in a row, Community High School District 155 received financial recognition from the Government Finance Officers and the Association of School Business Officials (ASBO) International for its June 30, 2019 Comprehensive Annual Financial Report (CAFR).

Steve Olson serves as Superintendent, and was appointed in August 2017.