| Index | Marietta | Illinois | National |
| Average Test Scores | n/a | 33% | 48% |
| Student/Teacher ratio | n/a | 18:1 | 16:1 |
| Total public schools | n/a | 3,938 | 79,221 |
| Total private schools | n/a | 1,438 | 24,874 |
| Total post-secondary schools | n/a | 306 | 7,963 |
| Index | Marietta | Illinois | National |
| Completed 8th grade | 77.9% | 86.2% | 84.3% |
| Completed high school | 72.1% | 84.7% | 83.0% |
| Completed some college | 30.2% | 61.8% | 59.4% |
| Completed associate degree | 18.6% | 40.7% | 38.5% |
| Completed bachelors | 12.8% | 32.9% | 30.3% |
| Completed masters | 11.6% | 12.7% | 11.5% |
| Completed professional degree | 0.0% | 3.4% | 3.3% |
| Completed doctorate | 0.0% | 1.2% | 1.3% |
There are a total of n/a public schools, n/a private schools and n/a post-secondary schools in Marietta. Using the proficiency score averages, the average test scores for Marietta, IL schools is n/a. The average student to teacher ratio is n/a. In Marietta, IL, an average of 77.9% of students have completed 8th grade and an average of 72.1% have completed high school.
| City | Population | Avg. Test Scores | National Avg. |
| London Mills, IL | 326 | 38% | 20.5% |
| Good Hope, IL | 405 | 35% | 27.1% |
| Cuba, IL | 1,066 | 27% | 43.1% |
| Lewistown, IL | 2,021 | 21% | 56.8% |
| Avon, IL | 690 | 18% | 63.5% |
| Marietta, IL | 61 | n/a |
| City | Population | Avg. Test Scores | National Avg. |
| Klukwan, AK | 61 | 50% | 4.2% |
| Yucca, AZ | 61 | 50% | 4.2% |
| Crookston, NE | 61 | 30% | 37.5% |
| St. Charles, VA | 61 | 83% | 71.9% |
| Menoken, ND | 61 | 60% | 25.0% |
| Marietta, IL | 61 | n/a |
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