| Abbreviation | Definition |
|---|---|
| OBHS | Oyster Bay High School |
| OBMS | Oakdale Bohemia Middle School |
| OBMS | Old Blacksburg Middle School |
| OBMS | Olive Branch Middle School |
| OBMS | Ormond Beach Middle School |
| OBSD | Ocean Beach School District |
| OBSS | Outward Bound School of Singapore |
| OBTS | Operation Back To School |
| OCAD | Ontario College of Art and Design |
| OCCS | Ohio Contemporary Chinese School |
| OCCS | Orange County Christian School |
| OCDSB | Ottawa Carleton District School Board |
| OCES | Oak Creek Elementary School |
| OCES | Ocean City Elementary School |
| OCES | Oconee County Elementary School |
| OCG | Orange Coast Gakuen |
| OCHS | Oak Creek High School |
| OCHS | Oaks Christian High School |
| OCHS | Ocean City High School |
| OCHS | Oconee County High School |