| Index | Castlewood | South Dakota | National |
| Average Test Scores | 34% | 43% | 49% |
| Student/Teacher ratio | n/a | 14:1 | 16:1 |
| Total public schools | n/a | 340 | 79,221 |
| Total private schools | n/a | 76 | 24,874 |
| Total post-secondary schools | n/a | 25 | 7,963 |
| Index | Castlewood | South Dakota | National |
| Completed 8th grade | 93.5% | 89.1% | 84.3% |
| Completed high school | 93.3% | 86.8% | 83.0% |
| Completed some college | 58.1% | 60.4% | 59.4% |
| Completed associate degree | 35.9% | 38.5% | 38.5% |
| Completed bachelors | 20.4% | 27.5% | 30.3% |
| Completed masters | 5.9% | 8.1% | 11.5% |
| Completed professional degree | 0.8% | 2.5% | 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 Castlewood. Using the proficiency score averages, the average test scores for Castlewood, SD schools is 34%. The average student to teacher ratio is n/a. In Castlewood, SD, an average of 93.5% of students have completed 8th grade and an average of 93.3% have completed high school.
| City, State | Population | Avg. Test Scores | National Avg. |
| Hayti, SD | 415 | 55% | 13% |
| Watertown, SD | 22,026 | 52% | 6% |
| Estelline, SD | 882 | 41% | 16% |
| Castlewood, SD | 609 | 34% | 31% |
| City, State | Population | Avg. Test Scores | National Avg. |
| Evansville, MN | 609 | 75% | 51% |
| Whitesburg, GA | 609 | 37% | 25% |
| New Washington, IN | 609 | 73% | 48% |
| Mathews, VA | 608 | 79% | 61% |
| Hanover, KS | 608 | 52% | 6% |
| Castlewood, SD | 609 | 34% | 31% |
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