Crystal Lake South High School, often referred to as "South" or "CLS," is one of three high schools in Crystal Lake, Illinois, and currently has a body of roughly 1916 students.
Serving 1,279 students in grades 9-12, Crystal Lake South High School ranks in the top 50% of all schools in Illinois for overall test scores (math proficiency is top 50%, and reading proficiency is top 50%).
The percentage of students achieving proficiency in math is 26% (which is lower than the Illinois state average of 27%). The percentage of students achieving proficiency in reading/language arts is 41% (which is higher than the Illinois state average of 30%).
The student-teacher ratio of 16:1 is higher than the Illinois state level of 13:1.
Minority enrollment is 35% of the student body (majority Hispanic), which is lower than the Illinois state average of 55% (majority Hispanic).
Quick Facts (2026-27)
- Grades: 9-12
- Enrollment: 1,279 students
- Student-Teacher Ratio: 16:1
- Minority Enrollment: 35%
- Graduation Rate: 94% (Top 20% in IL)
- Overall Testing Rank: Top 50%
- Math Proficiency: 26% (Top 50%)
- Reading Proficiency: 41% (Top 30%)
- Science Proficiency: 62% (Top 30%)
- Attendance Zone: Crystal Lake South High School serves the southwest part of Crystal Lake, IL, covering an area of approximately 6.3 square miles. Families typically have a drive of 5-10 minutes to the school, with the furthest edge of the attendance zone being about 2.4 miles away.
- Source: National Center for Education Statistics (NCES), IL Dept. of Education
Top Rankings
Crystal Lake South High School ranks among the top 20% of public schools in Illinois for:
Category
Attribute
Most improved public schools
Graduation Rate
School Overview
Crystal Lake South High School's student population of 1,279 students has declined by 9% over five school years.
The teacher population of 78 teachers has declined by 13% over five school years.
Grades Offered
Grades 9-12
Total Students
1,279 students
Total Classroom Teachers
78 teachers
Year Founded
1978
Colors
Green, Gold
School Calendar
Campus Size
50 acres
School Rankings
Crystal Lake South High School ranks within the top 50% of all 3,542 schools in Illinois (based off of combined math and reading proficiency testing data).
The diversity score of Crystal Lake South High School is 0.51, which is less than the diversity score at state average of 0.70. The school's diversity has stayed relatively flat over five school years.
Overall Testing Rank
#1137 out of 3542 schools
(Top 50%)
(Top 50%)
Math Test Scores (% Proficient)
26%
27%
Reading/Language Arts Test Scores (% Proficient)
41%
30%
Science Test Scores (% Proficient)
62%
50%
Student-Teacher Ratio
16:1
13:1
American Indian
n/a
n/a
Asian
4%
6%
Hispanic
26%
29%
Black
3%
16%
White
65%
45%
Hawaiian
n/a
n/a
Two or more races
2%
4%
All Ethnic Groups
Graduation Rate
94%
87%
Chronically Absent Students
(22-23)23.7%
29.7%
Eligible for Free Lunch
14%
43%
Eligible for Reduced Lunch
5%
4%
School Statewide Testing
School District Name
Source: National Center for Education Statistics (NCES), IL Dept. of Education
School Notes
- School Mascot: Alligators
Frequently Asked Questions
What is Crystal Lake South High School's ranking?
Crystal Lake South High School is ranked #1137 out of 3,542 schools, which ranks it among the top 50% of public schools in Illinois.
What schools are Crystal Lake South High School often compared to?
Crystal Lake South High Schoolis often viewed alongside schools like Crystal Lake Central High School, Huntley High School by visitors of our site.
What percent of students have achieved state testing proficiency in math and reading?
26% of students have achieved math proficiency (compared to the 27% IL state average), while 41% of students have achieved reading proficiency (compared to the 30% IL state average).
What is the graduation rate of Crystal Lake South High School?
The graduation rate of Crystal Lake South High School is 94%, which is higher than the Illinois state average of 87%.
How many students attend Crystal Lake South High School?
1,279 students attend Crystal Lake South High School.
What is the racial composition of the student body?
65% of Crystal Lake South High School students are White, 26% of students are Hispanic, 4% of students are Asian, 3% of students are Black, and 2% of students are Two or more races.
What is the student-teacher ratio of Crystal Lake South High School?
Crystal Lake South High School has a student ration of 16:1, which is higher than the Illinois state average of 13:1.
What grades does Crystal Lake South High School offer ?
Crystal Lake South High School offers enrollment in grades 9-12
What school district is Crystal Lake South High School part of?
Crystal Lake South High School is part of CHSD 155 School District.
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