KSHSAA divides schools based upon enrollment of grades 9, 10, 11 and 12 for competition and state and regional championships. The largest 32 schools in the state are class 6A, the next largest 32 become 5A, the next 64 become 4A, 3A, and 2A respectively and the remaining schools become class 1A. These classes are re-evaluated every year for all activities except football, with new classifications announced in September after the start of the school year. Ninth grade students were not counted toward the annual classification totals from 1967 to 1968 through 2010–11. In 2013, the 64 schools in class 4A voted to split into two divisions for volleyball, baseball, basketball, softball, and football.
Starting with the 2018–19 school year, Classes 6A, 5A and 4A consist of 36 schools each. Classes 3A and 2A continue to have 64 schools each, while the remaining schools will be in 1A. The two-division format which currently exists in 1A for basketball, scholars bowl and volleyball, and in 4A for baseball, basketball, softball and volleyball, were eliminated; however, the two-division structure in 1A was reinstated by a vote of 1A members for the 2020-21 school year.
Football is evaluated biannually based only upon enrollment for grades 9, 10, and 11, with classifications for the next two seasons announced in October of an odd-numbered year. Schools with 100 or fewer students in grades 9-11 have the option to play Eight-man football instead of the traditional 11-man game. In 11-man football, there are five classes (6A, 5A, 4A, 3A, 2-1A), with 32 schools in 6A and 5A, 64 schools in 4A and 3A, and the remaining schools (43 for 2010 and 2011; 41 for 2012 and 2013) in 2-1A. In eight-man football, there are two divisions of roughly equal size, with 105 schools scheduled to compete in 8-man for the 2010 and 2011 seasons, decreasing to 104 for 2012 and 2013 due to consolidation in many rural towns.
Beginning in 2018, Classes 6A, 5A and 4A will have 32 schools in each classification for football, with the two-division format in 4A eliminated. Classes 3A and 2A will have 48 schools each, and Class 1A will have the remaining 11-man football playing schools (31 in 2018 and 2019). 8-man Division I will be limited to 48 schools, with the remainder in 8-man Division II.
Football classifications were revamped again in 2022. Classes 6A, 5A and 4A remained unchanged, but 3A and 2A were reduced from 48 schools each to 40, with the remaining 11-man schools competing in 1A. This expanded the number of 1A schools from 28 in 2020 and 2021 to 42 in 2022 and 2023. Additionally, the KSHSAA began to sponsor 6-man football in 2022 for schools with 55 students or fewer in grades 9-11 at the time of reclassification.