Crystal Lake South High School

Crystal Lake South High School, a high-enrollment secondary school in Crystal Lake, Illinois, run under CHSD 155, works with 1,279 students, covering grades 9 through 12. By comparison, Illinois's public schools average about 834 students each, so Crystal Lake South High School sits 53% larger than that benchmark.

Across the 4 schools in CHSD 155 (5,203 students total), Crystal Lake South High School accounts for its share of the district's footprint.

Demographically, Crystal Lake South High School logs that the largest single group is White, at 65% of enrollment. The remainder breaks down as 26% Hispanic, 4% Asian, 3% Black, 2% multiracial. By comparison, McHenry County as a whole is about 80% White, so the school skews noticeably less White than its surroundings.

On the resource side, On paper, Crystal Lake South High School has 78 full-time-equivalent teachers, translating to a class-load average of around 16.5:1. The state averages around 13.8:1, so this campus is higher than the state norm typical. An estimated 32% of students are eligible for free or reduced-price lunch, often used as a Title I proxy.

On a residual basis (actual vs predicted given the student mix), Crystal Lake South High School tracks the demographic baseline. The model predicts 53.0% given the school's FRL share; actual proficiency is 46.5%.

Around the school, the surrounding county (McHenry County) logs that the typical household earns roughly $104,802 per year, about 35% of the adult population holds a bachelor's degree or above, and roughly 4% of residents live below the federal poverty line. Crystal Lake South High School is one of 89 public schools in McHenry County (combined enrollment of about 50,123 students).

The closest other public school is Coventry Elem School, roughly 0.8 miles away. Counting just inside five miles, 8 other public schools cluster around Crystal Lake South High School. Among the 9 schools in that immediate cluster with test data (this one included), Crystal Lake South High School ranks 5th on composite proficiency, behind the local average of 46.5%.

The school occupies a bedroom-community site.

Looking at the recent track record. Crystal Lake South High School's enrollment has shrank 13% since 2018, when it stood at 1,462 (now 1,279). White enrollment moved from 83% to 65% across the same window. Class-load math has pulled in: from 17.7:1 in 2018 to 16.5:1 in 2025.

On allk12, the page collects discussion, questions, and updates around school events, parent volunteer needs, and clubs. Parents, students, alumni, and staff are welcome to weigh in.