Prior to 1978, one high school, Crystal Lake Community High School, housed all students in Crystal Lake and was constructed in 1927. With increasing population, however, residents passed a referendum to build Crystal Lake South which opened in the fall of 1978, with the first graduating class of 1979.
In 2002, enrollment was approaching 1600, so construction began on a new addition to add classrooms by connecting two of the spokes. Also, remodeling projects widened the halls, moved nearly all the faculty into a large faculty office, and centralized the computer labs. This addition also added a lower level, which will open in fall of 2006. There are currently 1900 students and 125 staff members at Crystal Lake South High School