| Index | St. Mary | Missouri | National |
| Average Test Scores | n/a | 44% | 48% |
| Student/Teacher ratio | n/a | 14:1 | 16:1 |
| Total public schools | n/a | 1,899 | 79,221 |
| Total private schools | n/a | 531 | 24,874 |
| Total post-secondary schools | n/a | 213 | 7,963 |

| Index | St. Mary | Missouri | National |
| Completed 8th grade | 81.8% | 86.0% | 84.3% |
| Completed high school | 78.1% | 84.2% | 83.0% |
| Completed some college | 35.8% | 57.7% | 59.4% |
| Completed associate degree | 18.2% | 35.2% | 38.5% |
| Completed bachelors | 11.3% | 27.6% | 30.3% |
| Completed masters | 7.3% | 10.4% | 11.5% |
| Completed professional degree | 2.6% | 2.8% | 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 St. Mary. Using the proficiency score averages, the average test scores for St. Mary, MO schools is n/a. The average student to teacher ratio is n/a. In St. Mary, MO, an average of 81.8% of students have completed 8th grade and an average of 78.1% have completed high school.
| City | Population | Avg. Test Scores | National Avg. |
| Ste. Genevieve, MO | 4,497 | 59% | 22.2% |
| Bloomsdale, MO | 858 | 57% | 18.8% |
| Perryville, MO | 8,741 | 41% | 14.2% |
| Evansville, IL | 790 | 40% | 17.7% |
| Chester, IL | 8,448 | 27% | 43.2% |
| St. Mary, MO | 266 | n/a |
| City | Population | Avg. Test Scores | National Avg. |
| Trenton, NC | 266 | 43% | 10.8% |
| Bovill, ID | 266 | 60% | 25.0% |
| Loganville, WI | 266 | 70% | 45.8% |
| Kingston, MO | 266 | 20% | 58.3% |
| Peetz, CO | 266 | 38% | 21.9% |
| St. Mary, MO | 266 | n/a |