Murder on the Blackboard: Hildegarde Withers, Book 3 (Unabridged‪)‬

Hildegarde Withers, schoolteacher and amateur detective, stumbles onto the corpse of Jefferson Grammar School's attractive young music teacher. When Miss Withers goes for help, the body plays hooky, and when Homicide Inspector Oscar Piper starts to investigate, somebody tries to brain him with a shovel. The rest of the cops want to throw the book at the school janitor, who has flunked their pop quiz. But Miss Withers disagrees and decides to stay after school to ask her own questions.