| Index | Water Mill | New York | National |
| Average Test Scores | n/a | 56% | 48% |
| Student/Teacher ratio | n/a | n/a | 16:1 |
| Total public schools | n/a | 4,060 | 79,221 |
| Total private schools | n/a | 1,092 | 24,874 |
| Total post-secondary schools | n/a | 483 | 7,963 |
| Index | Water Mill | New York | National |
| Completed 8th grade | 96.9% | 83.5% | 84.3% |
| Completed high school | 96.4% | 82.1% | 83.0% |
| Completed some college | 78.7% | 59.5% | 59.4% |
| Completed associate degree | 65.9% | 43.4% | 38.5% |
| Completed bachelors | 59.5% | 34.7% | 30.3% |
| Completed masters | 31.5% | 15.1% | 11.5% |
| Completed professional degree | 12.4% | 4.2% | 3.3% |
| Completed doctorate | 2.1% | 1.5% | 1.3% |
There are a total of n/a public schools, n/a private schools and n/a post-secondary schools in Water Mill. Using the proficiency score averages, the average test scores for Water Mill, NY schools is n/a. The average student to teacher ratio is n/a. In Water Mill, NY, an average of 96.9% of students have completed 8th grade and an average of 96.4% have completed high school.
| City | Population | Avg. Test Scores | National Avg. |
| Amagansett, NY | 510 | 80% | 66.7% |
| Quogue, NY | 600 | 80% | 66.7% |
| Mattituck, NY | 4,898 | 77% | 60.4% |
| Sag Harbor, NY | 1,959 | 65% | 34.4% |
| East Hampton, NY | 920 | 63% | 31.0% |
| Water Mill, NY | 1,860 | n/a |
| City | Population | Avg. Test Scores | National Avg. |
| Port Henry, NY | 1,859 | 48% | 0.5% |
| Capac, MI | 1,858 | 40% | 16.3% |
| Orwell, OH | 1,862 | 65% | 34.4% |
| Harbor Beach, MI | 1,862 | 52% | 7.6% |
| Marriott-Slaterville, UT | 1,862 | 35% | 27.1% |
| Water Mill, NY | 1,860 | n/a |
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