How to read this list
Each school is scored on its most recent year carrying both a math and a reading (English Language Arts) all-students proficiency figure on Illinois's native assessment. The final column is the difference: math proficiency minus reading proficiency, in percentage points. A negative number means a school's students are more often proficient in reading than in math; a positive number means the reverse. Because both figures come from the same students taking the same test under the same cut-score policy, the gap is an apples-to-apples comparison in a way that raw cross-state proficiency rates are not.
A wide gap is not automatically a problem. Arts, language-immersion, and humanities-focused programs often post strong reading and weaker math; STEM and career-technical programs often do the reverse. But a persistent, schoolwide divergence is worth a parent's attention, because it can also flag a staffing gap, a curriculum weakness, or a math-anxiety culture that a single year of scores would hide.
What is excluded
Brick-and-mortar schools only: virtual academies and cyber charters are removed because their results are noisy and rarely reflect a school families choose geographically. Specialized-population schools (state schools for the deaf or blind, therapeutic and juvenile-justice placements, and NCES special-education or alternative-education campuses) are also excluded, because state proficiency rates are not a comparable metric for them. Schools must have at least 150 students and at least 5% proficient in each subject, a floor that drops suppression and coding artifacts.
Source data
Illinois state assessment results loaded into allk12, joined to the NCES Common Core of Data school directory. Refreshed when the state publishes a new assessment file. See the national report for the state-by-state summary.