| MCHS | Madison Co High School 
| Others |
| MCHS | Madison Consolidated High School
| Others |
| MCHS | Madison County High School
| Others |
| MCHS | Malden Catholic High School
| Others |
| MCHS | Manheim Central High School
| Others |
| MCHS | Manitowoc County Historical Society
| Others |
| MCHS | Manor Care Health Services
| Others |
| MCHS | Marengo Community High School
| Others |
| MCHS | Maria Carrillo High School
| Others |
| MCHS | Marian Catholic High School
| Others |
| MCHS | Mariposa County High School
| Others |
| MCHS | Marquette Catholic High School
| Others |
| MCHS | Marshall County High School
| Others |
| MCHS | Martin County High School
| Others |
| MCHS | Marystown Central High School
| Others |
| MCHS | Massac County High School
| Others |
| MCHS | Mayde Creek High School
| Others |
| MCHS | Mayo Clinic Health System
| Others |
| MCHS | Mcauley Catholic High School
| Others |
| MCHS | Meade County High School
| Others |
| MCHS | Mearns Castle High School
| Others |
| MCHS | Memorial Composite High School
| Others |
| MCHS | Meols Cop High School
| Others |
| MCHS | Merced County Humane Society
| Others |
| MCHS | Mercy College of Health Sciences
| Others |
| MCHS | Methodist Children's Home Society
| Others |
| MCHS | Michigan City High School
| Others |
| MCHS | Middle College High School
| Others |
| MCHS | Middle Creek High School
| Others |
| MCHS | Midwest City High School
| Others |
| MCHS | Mifflin County High School
| Others |
| MCHS | Mill Creek High School
| Others |
| MCHS | Millington Central High School
| Others |
| MCHS | Minooka Community High School
| Others |
| MCHS | Mira Costa High School
| Others |
| MCHS | Mission Collegiate High School
| Others |
| MCHS | Monkseaton Community High School
| Others |
| MCHS | Monroe Catholic High School
| Others |
| MCHS | Monroe Central High School
| Others |
| MCHS | Montezuma Cortez High School
| Others |
| MCHS | Montgomery County Humane Society
| Others |
| MCHS | Moore Catholic High School
| Others |
| MCHS | Morgan City High School
| Others |
| MCHS | Morgan County High School
| Others |
| MCHS | Morinville Community High School
| Others |
| MCHS | Morris Community High School
| Others |
| MCHS | Mount Carmel High School
| Others |
| MCHS | Mt Carmel High School
| Others |
| MCHS | myocerebrohepatopathy spectrum
| Others |
| MCHS | myocerebrohepatopathy syndrome
| Others |