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 1,291 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 17:1 is higher than the Illinois state level of 13:1.
Minority enrollment is 32% of the student body (majority Hispanic), which is lower than the Illinois state average of 55% (majority Hispanic).
Quick Facts (2025)
- Grades: 9-12
- Enrollment: 1,291 students
- Student-Teacher Ratio: 17:1
- Minority Enrollment: 32%
- 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%)
- 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 1,291 students has declined by 12% over five school years.
The teacher population of 75 teachers has declined by 16% over five school years.
Grades Offered
Grades 9-12
Total Students
1,291 students
Gender %
Total Classroom Teachers
75 teachers
Year Founded
1978
Colors
Green, Gold
School Calendar
Last Day of School
Sat. Jun 6, 2026
Campus Size
50
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 0.48, 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
17:1
13:1
American Indian
n/a
1%
Asian
4%
6%
Hispanic
24%
28%
Black
3%
16%
White
68%
45%
Hawaiian
n/a
n/a
Two or more races
1%
4%
All Ethnic Groups
Graduation Rate
94%
87%
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
Profile last updated: 02/09/2025
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?
1,291 students attend Crystal Lake South High School.
What is the racial composition of the student body?
68% of Crystal Lake South High School students are White, 24% of students are Hispanic, 4% of students are Asian, 3% of students are Black, and 1% 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 17:1, 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.
School Reviews
Review Crystal Lake South High School. Reviews should be a few sentences in length. Please include any comments on:
- Quality of academic programs, teachers, and facilities
- Availability of music, art, sports and other extracurricular activities
Recent Articles
Why Single-Sex Public Schools are Growing in Popularity
This article examines the growing trend of single-sex public schools in the United States. It explores the potential benefits, research findings, and controversies surrounding gender-specific education, as well as the factors driving its increasing popularity among parents and educators.
When Teachers Cheat: The Standardized Test Controversies
Teachers across the country are being accused of cheating on standardized tests, using erasers to conveniently change their students’ answers. However, are these teachers driven to cheat because the funding system is flawed?
When Field Trips Turn Deadly: Who is Responsible?
Recent deaths during field trips have parents and school officials questioning the safety of these excursions. Learn about these tragedies and what parameters should be in place to ensure a safe field trip.
