| Abbreviation | Definition |
|---|---|
| OHSC | Of Hours School Care |
| OHSC | Ontario Healthy Schools Coalition |
| OHSC | Ouran High School Club |
| OHSC | Out of Hours School Care |
| OHSP | Open High School Program |
| OHSU | Open High School of Utah |
| OHTS | Oxford Hills Technical School |
| OIA | Oakland International Academy |
| OIMS | Olean Intermediate Middle School |
| OIS | Orinda Intermediate School |
| OIS | Oxford Intermediate School |
| OISD | Orcas Island School District |
| OISR | Office of Innovation and School Reform |
| OJH | Flint Open Jr. High School |
| OJH | Flint Open Junior High School |
| OJH | Oakdale Junior High School |
| OJH | Odem Junior High School |
| OJH | Orland Jr. High School |
| OJH | Orland Junior High School |
| OJH | Osseo Junior High School |