| Abbreviation | Definition |
|---|---|
| MCGS | Mayo College Girls School |
| MCHCS | Monterey County Home Charter School |
| MCHS | Madison Co High School |
| MCHS | Madison Consolidated High School |
| MCHS | Madison County High School |
| MCHS | Manheim Central High School |
| MCHS | Marengo Community High School |
| MCHS | Maria Carrillo High School |
| MCHS | Mariposa County High School |
| MCHS | Marshall County High School |
| MCHS | Martin County High School |
| MCHS | Marystown Central High School |
| MCHS | Massac County High School |
| MCHS | Mayde Creek High School |
| MCHS | Meade County High School |
| MCHS | Mearns Castle High School |
| MCHS | Memorial Composite High School |
| MCHS | Meols Cop High School |
| MCHS | Michigan City High School |
| MCHS | Middle College High School |