| Abbreviation | Definition |
|---|---|
| OSSM | Oklahoma School of Science and Mathematics |
| OSSTF | Ontario Secondary School Teachers' Federation |
| OST | Oblate School of Theology |
| OST | Out of School Time |
| OSTC | Oakland Schools Technical Campus |
| OSTC | Oakland Schools Technical Campuses |
| OSTM | Onondaga School of Therapeutic Massage |
| OSTN | Oakland Schools Television Network (Waterford, MI) |
| OSTN | Out-of-School Time Network (Boston, MA) |
| OSTP | Oklahoma School Testing Program |
| OSW | Old School Works |
| OTDS | Ontario Truck Driving School |
| OTHS | Oakland Technical High School |
| OTHS | Oakville Trafalgar High School |
| OTHS | Obra D Tompkins High School |
| OTHS | Ocean Township High School |
| OTHS | O'Fallon Township High School |
| OTHS | Old Tappan High School |
| OTHS | Old Town High School |
| OTHS | Osgoode Township High School |