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Class Sizes

CTU analysis shows Chicago's school class sizes are among the highest in the state

Download a one-page fact sheet on class size here.

For legislative information on class size click here.

Download an additional fact sheet here.

Links to more research can be found here.

The CTU analysis also found:

  • Out of the 480 Illinois school districts with high schools, Chicago has the fifth largest average high-school class size. The only districts with larger average high school class sizes are in Woodstock, Pikeland, Havana and Oaklawn.
  • Chicago’s average class sizes at the early childhood grades (k-1) are larger than 95 percent of all Illinois school districts.
  • Upon average across all elementary grades, Chicago has the 14th highest class size averaged across the elementary grades (k-8).

“Reducing class sizes can lead to improved teaching and learning,” said CTU President Karen GJ Lewis. “In a smaller classroom, a teacher has more time to get to know each student's academic strengths and weaknesses; students receive more attention and teachers can spend more time helping students learn and working with parents.”

Tennessee’s Project STAR (Student Teacher Achievement Ratio) found that smaller class sizes had positive effects at every grade level across all school locations (rural, urban, inner city, suburban), on every achievement measure and for all subjects (reading, mathematics, science, social science, language, study skills).

The study also found that students assigned to small classes of 15 students  in early grades graduated on schedule at a higher rate (76 %) than students from regular classes  of 24 (64%).  The same students also completed school with an honors diploma more often than students from regular classes and dropped out of school less often (15 %) compared to the regular classes (24%).

Recently, parents have contacted CTU about concerns about class size. Until early October one third grade classroom at Cassell Elementary, 11314 S. Spaulding, had 42 students in a single class. The matter was resolved internally when the administration and teachers agreed to develop a second/third grade split class. Chicago is the only district whose union is not allowed to bargain over class size. The 1995 School Reform Act included a list of topics that were either prohibited or permissive of bargaining, meaning the Union can bargain over the impact of class size but the not actual class size. 

“We know from studies and teacher experience that particularly at the lower grade level, students in smaller classes get off to a better start in their schooling because the teacher is able to modify her instruction to meet the needs of individual children and better communicate with their parents,” said CTU researcher Carol Caref.


The Chicago Teachers Union represents 30,000 teachers and educational support personnel working in the Chicago Public Schools and, by extension, the students and families they serve. CTU, an affiliate of the American Federation of Teachers and the Illinois Federation of Teachers, is the third largest teachers local in the country and the largest local union in Illinois. For more information visit CTU’s website at

Chicago Teachers Union