| Index | Selden | New York | National |
| Average Test Scores | 48% | 56% | 48% |
| Student/Teacher ratio | n/a | n/a | 16:1 |
| Total public schools | 5 | 4,060 | 79,221 |
| Total private schools | 1 | 1,092 | 24,874 |
| Total post-secondary schools | 1 | 483 | 7,963 |
| Index | Selden | New York | National |
| Completed 8th grade | 85.5% | 83.5% | 84.3% |
| Completed high school | 85.1% | 82.1% | 83.0% |
| Completed some college | 54.7% | 59.5% | 59.4% |
| Completed associate degree | 35.9% | 43.4% | 38.5% |
| Completed bachelors | 23.9% | 34.7% | 30.3% |
| Completed masters | 9.4% | 15.1% | 11.5% |
| Completed professional degree | 1.9% | 4.2% | 3.3% |
| Completed doctorate | 0.9% | 1.5% | 1.3% |
There are a total of 5 public schools, 1 private schools and 1 post-secondary schools in Selden. Using the proficiency score averages, the average test scores for Selden, NY schools is 48%. The average student to teacher ratio is n/a. In Selden, NY, an average of 85.5% of students have completed 8th grade and an average of 85.1% have completed high school.
| City | Population | Avg. Test Scores | National Avg. |
| Shoreham, NY | 375 | 82% | 69.8% |
| West Sayville, NY | 4,956 | 82% | 69.8% |
| Hauppauge, NY | 19,661 | 80% | 66.3% |
| Setauket-East Setauket, NY | 14,174 | 80% | 65.6% |
| Port Jefferson, NY | 8,016 | 77% | 60.8% |
| Selden, NY | 21,338 | 48% | 0.8% |
| City | Population | Avg. Test Scores | National Avg. |
| Cartersville, GA | 21,331 | 45% | 6.1% |
| Mountlake Terrace, WA | 21,328 | 66% | 36.7% |
| La Porte, IN | 21,328 | 49% | 2.7% |
| Mountain House, CA | 21,387 | 69% | 42.9% |
| Oxford, AL | 21,282 | 52% | 7.3% |
| Selden, NY | 21,338 | 48% | 0.8% |
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