| Abbreviation | Definition |
|---|---|
| CIHS | Cambridge Isanti High School |
| CIHS | Cambridge-Isanti High School |
| CIHS | Channel Islands High School |
| CIHS | College in the High School |
| CIHS | Cooperative Innovative High Schools |
| CILS | Center for Informal Learning and Schools |
| CILS | Center for Informal Learning in Schools |
| CIMS | Corwin International Magnet School |
| CINS | Council of Intown Neighborhoods and Schools |
| CIPS | Cosmetology Instructors of Public Schools |
| CIPS | Covington Independent Public Schools |
| CIRAS | Croatian International Rhinosurgical Advanced School |
| CIRHS | Calicut Islamic Residential High School |
| CIS | Combat In School |
| CIS | Commission on Independent Schools |
| CIS | Communities In the Schools |
| CIS | Cuba Independent Schools |
| CISAC | Connecticut Independent School Athletic Conference |
| CISC | Catholic Independent Schools Conference |
| CISD | Canutillo Independent School District |