High school (grades 9-12) · O Fallon, IL
O Fallon High School
Federal NCES profile for O Fallon High School, including enrollment, faculty, free-lunch eligibility, demographics, and resource indicators - Resource Investment Index 36/100.
The verdict
O Fallon High School earns 36/100 on the Resource Investment Index, with class sizes larger than 87% of Illinois schools. It is also one of the largest schools in Illinois.
- #6 of 10
- public schools in O Fallon · Resource Index
- 36
- Resource Index · Typical
- 17:1
- large classes for Illinois
- 2,540
- students enrolled
O Fallon High School has class sizes larger than 87% of Illinois schools. Computed live against every Illinois school reporting to NCES.
By Resource Investment Index, O Fallon High School ranks #6 of 10 public schools in O Fallon, IL.
School address
NCES ID 172979003090 Verify on NCES CCD record →
NCES CCD universe card
School universe 172979003090 · O Fallon, IL High · LARGE · TRAD
2,540 enr · 17:1 · RII 36
Nearest enrollment peer: Ruben S. Ayala High (2,541 students)
Resource Investment Index #6 of 10 public schools in O Fallon. NCES Common Core of Data stamps for this campus. Read with this school → · District book → · Illinois schools → · Find another →
How O Fallon High School compares
O Fallon High School on the metrics families compare, against Illinois and U.S. means.
| Metric | This school | vs Illinois | Illinois avg | U.S. avg |
|---|---|---|---|---|
| Students per teacher | 17:1 | ▲ 21% | 14:1 | 15.7:1 |
| Enrollment | 2,540 | top 1% | - | - |
Source: NCES Common Core of Data School-level CCD + state/national means from Public School Universe · 2024-25
Equity indicators (what these measure)
Student demographics
Largest group: White at 59.3% of enrollment.
Simpson diversity index - at 59.0, O Fallon High School is more mixed than the Illinois school average of 38.9.
Programs
Funding & spending
District-wide per-pupil expenditure for O Fallon Twp Hsd 203, which includes O Fallon High School.
Source: NCES F-33 School District Finance Survey District-level finance · FY 2022-23 Per-pupil expenditure reflects the district-wide average. Individual school budgets are not reported at the federal level.
Nationwide high schools with similar size or staffing
Out-of-state peers matched by enrollment and by student-teacher ratio, not the same-city or same-district lists above.
Similar enrollment (~2,540 students)
Similar student-teacher ratio (~17:1)
Frequently asked questions about O Fallon High School
How many students attend O Fallon High School?
O Fallon High School has 2,540 students enrolled. It is a high school in O Fallon, IL.
What is the student-teacher ratio at O Fallon High School?
The student-teacher ratio at O Fallon High School is 17:1, which is 21% higher than the Illinois average of 14:1 and 8% higher than the national average of 15.7:1.
What is the racial and ethnic makeup of O Fallon High School?
The largest demographic group at O Fallon High School is White at 59.3% of enrollment, in O Fallon, IL. Its student body is more racially and ethnically mixed than most US schools, with a diversity index of 59.0/100.
What is the Resource Investment Index for O Fallon High School?
O Fallon High School has a Resource Investment Index of 36/100 (typical reported resources relative to schools nationally) based on 4 factors: student-teacher ratio, gifted-program reporting, counselor availability, chronic absenteeism. Not a test-score or academic measure (national median ~41/100, see methodology).
How does O Fallon High School rank among public schools in O Fallon?
By Resource Investment Index, O Fallon High School ranks #6 of 10 public schools in O Fallon, IL. This compares federal resource and staffing data among local peers; it is not a test-score or academic ranking. See all public schools in O Fallon on the city page.
What other schools are in O Fallon Twp Hsd 203?
None reported; O Fallon Twp Hsd 203 operates only O Fallon High School as a public school district in NCES's records.
Every figure on PlainSchools is rendered directly from the source NCES, CRDC and F-33 federal records, no number is typed in by an editor. Each school's figures reflect its most recent NCES/CRDC submission on file. See our editorial standards & corrections policy, the methodology behind these numbers, the data changelog, or report a data error. Data current as of August 2026.