| Pepperell Christian Academy | 3.3 |
Regular elementary or secondary | Pre-KG-12 | 29 | 5.5 | Baptist |
| Mary Mcleod Bethune Institute | 4.3 |
Special program emphasis | 3-12 | 45 | 8.0 | Nonsectarian |
| Seven Hills Academy | 5.5 |
Special education | 4-12 | 60 | 14.6 | Nonsectarian |
| Nashoba Learning Group | 5.9 |
Special education | Pre-KG-11 | 40 | 0.8 | Nonsectarian |
| Twin City Christian School | 9.0 |
Regular elementary or secondary | Pre-KG-12 | 191 | 12.2 | Baptist |
| Lighthouse School | 9.9 |
Special education | Pre-KG-12 | 220 | 6.7 | Nonsectarian |
| Applewild School | 11.7 |
Regular elementary or secondary | KG-9 | 282 | 7.8 | Nonsectarian |
| Riverside School | 12.2 |
Special education | 2-12 | 34 | 4.9 | Nonsectarian |
| Rfk Lancaster School | 12.5 |
Special education | 4-12 | 36 | 1.1 | Nonsectarian |
| Merrimack Schools | 12.7 |
Alternative/other | 5-12 | 55 | 2.5 | Nonsectarian |
| South Lancaster Academy And Browning Elementary | 12.7 |
Regular elementary or secondary | Pre-KG-12 | 237 | 15.0 | Seventh-Day Adventist |
| Sterling Nursery School | 14.7 |
Special education | Pre-KG-Pre-KG | 3 | 0.8 | Nonsectarian |
| The Fenn School | 15.0 |
Regular elementary or secondary | 4-9 | 304 | 8.2 | Nonsectarian |
| Willow Hill School | 16.3 |
Special education | 6-12 | 60 | 3.4 | Nonsectarian |
| Melmark New England | 17.3 |
Special education | Ungraded-Ungraded | 108 | 1.5 | Nonsectarian |
| Hillside School | 18.1 |
Regular elementary or secondary | 5-9 | 139 | 6.0 | Nonsectarian |
| Fellowship Christian Academy | 20.2 |
Regular elementary or secondary | Pre-KG-12 | 108 | 10.8 | Christian (no specific denomination) |
| St Ann's Home Inc | 20.5 |
Special education | Ungraded-Ungraded | 122 | 6.7 | Nonsectarian |
| Sudbury Valley School | 20.8 |
Special program emphasis | Ungraded-Ungraded | 165 | 16.7 | Nonsectarian |
| Reed Academy | 20.8 |
Special education | Ungraded-Ungraded | 20 | 3.4 | Nonsectarian |
| Community Therapeutic Day School Inc | 21.3 |
Special education | Ungraded-Ungraded | 30 | 2.6 | Nonsectarian |
| Fay School | 21.3 |
Regular elementary or secondary | 1-9 | 379 | 6.6 | Nonsectarian |
| Cotting School | 21.9 |
Special education | Ungraded-Ungraded | 119 | 4.8 | Nonsectarian |
| New England Center For Children | 22.2 |
Special education | Pre-KG-12 | 191 | 2.3 | Nonsectarian |
| Open Bible Academy | 22.5 |
Regular elementary or secondary | Pre-KG-12 | 71 | 6.2 | Christian (no specific denomination) |
| The Learning Center For The Deaf | 22.5 |
Special education | Pre-KG-12 | 184 | 4.3 | Nonsectarian |
| The Pike School | 22.6 |
Regular elementary or secondary | Pre-KG-9 | 418 | 9.1 | Nonsectarian |
| The Gifford School | 22.8 |
Special education | 4-12 | 106 | 4.8 | Nonsectarian |
| Lexington Christian Academy | 23.1 |
Regular elementary or secondary | 6-12 | 345 | 9.9 | Christian (no specific denomination) |
| Brandon Residential Treatment | 23.7 |
Special education | 1-11 | 74 | 5.9 | Nonsectarian |
| The Rivers School | 23.9 |
Regular elementary or secondary | 6-12 | 433 | 7.5 | Nonsectarian |
| Germaine Lawrence | 24.0 |
Alternative/other | 6-12 | 50 | 4.5 | Nonsectarian |
| Crossroad Center For Children | 24.0 |
Special education | Ungraded-Ungraded | 40 | 5.7 | Nonsectarian |
| Bancroft School | 24.5 |
Regular elementary or secondary | KG-12 | 562 | 7.7 | Nonsectarian |
| Cottage Hill Academy | 24.6 |
Special education | 6-12 | 32 | 4.0 | Nonsectarian |
| Protestant Guild Learning Center | 24.7 |
Special education | 5-12 | 38 | 2.3 | Nonsectarian |
| Protestant Guild For Human Services | 24.7 |
Special education | Ungraded-Ungraded | 60 | 6.1 | Nonsectarian |
| Mercy Centre | 24.9 |
Special education | Ungraded-Ungraded | 24 | 6.0 | Roman Catholic |
