Cast (in credits order) verified as complete
| Edna May Oliver | Hildegarde Withers |
| James Gleason | Inspector Oscar Piper |
| Bruce Cabot | Addison 'Ad' Stevens |
| Gertrude Michael | Jane Davis |
| Regis Toomey | Detective Smiley North |
Full Answer
A popular cozy mystery series, The Hildegarde Withers Mysteries, by Stuart Palmer, includes Murder on the Blackboard, set in New York City in the 1930s, at a time when teaching positions were often given to unmarried women because "they needed the work”, and a time when, generally speaking, teachers were much more prim and proper than today.