| Index | O'Fallon | Illinois | National |
| Average Test Scores | 48% | 33% | 48% |
| Student/Teacher ratio | n/a | 18:1 | 16:1 |
| Total public schools | n/a | 3,938 | 79,221 |
| Total private schools | 3 | 1,438 | 24,874 |
| Total post-secondary schools | n/a | 306 | 7,963 |
| Index | O'Fallon | Illinois | National |
| Completed 8th grade | 95.3% | 86.2% | 84.3% |
| Completed high school | 95.0% | 84.7% | 83.0% |
| Completed some college | 79.2% | 61.8% | 59.4% |
| Completed associate degree | 58.1% | 40.7% | 38.5% |
| Completed bachelors | 46.1% | 32.9% | 30.3% |
| Completed masters | 20.9% | 12.7% | 11.5% |
| Completed professional degree | 3.7% | 3.4% | 3.3% |
| Completed doctorate | 1.4% | 1.2% | 1.3% |
There are a total of n/a public schools, 3 private schools and n/a post-secondary schools in O'Fallon. Using the proficiency score averages, the average test scores for O'Fallon, IL schools is 48%. The average student to teacher ratio is n/a. In O'Fallon, IL, an average of 95.3% of students have completed 8th grade and an average of 95.0% have completed high school.
| City | Population | Avg. Test Scores | National Avg. |
| St. Jacob, IL | 1,529 | 67% | 39.6% |
| Maryville, IL | 7,962 | 65% | 34.4% |
| Smithton, IL | 4,019 | 61% | 27.1% |
| Glen Carbon, IL | 12,468 | 57% | 18.8% |
| Freeburg, IL | 3,911 | 55% | 14.1% |
| O'Fallon, IL | 29,487 | 48% | 0.1% |
| City | Population | Avg. Test Scores | National Avg. |
| Crofton, MD | 29,482 | 65% | 34.9% |
| Canton, GA | 29,459 | 57% | 18.4% |
| Suisun City, CA | 29,459 | 33% | 31.8% |
| Seguin, TX | 29,458 | 41% | 15.6% |
| East Palo Alto, CA | 29,448 | 22% | 53.9% |
| O'Fallon, IL | 29,487 | 48% | 0.1% |
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