| Abbreviation | Definition |
|---|---|
| ACSP | Association of Collegiate Schools of Planning |
| ACSR | Antioch Center for School Renewal |
| ACST | American Cooperative School of Tunis |
| ACSU | Algemene Chinese school Utrecht |
| ACSW | AcadeMir Charter School West |
| ACT | American Conservatory Theater |
| ACTS | Announcing Christ To Schools |
| ACTS | Apostolic Center for Training and Service |
| ACTS | Associated Canadian Theological Schools |
| ACTS | Association of Christian Teachers and Schools |
| ACTS | Auckland City Training School |
| ACYI | Alvin C. York Institution |
| ADGSS | Army Day Girls Secondary School |
| ADHD | Attention Deficit/Hyperactivity Disorder |
| ADHS | Acton District High School |
| ADHS | Alfred Deakin High School |
| ADHS | Almonte and District High School |
| ADHS | Arnprior District High School |
| ADHS | Athens District High School |
| ADHS | Athens Drive High School |