Our Teacher Is a Vampire and Other (Not) True Stories — Mary Amato

It all begins when Alexander H. Gory Jr. passes around a notebook in which he reveals a tantalizing secret: he has proof that their teacher, Mrs. Penrose, is a vampire. Soon the entire class is speculating and adding their opinions to the notebook until ... it lands in Mrs. Penrose's hands. It turns out that Mrs. Penrose has been keeping a secret: she is expecting a baby. But since the notebook is encouraging her students to write and improving their spelling and grammar, Mrs. Penrose allows it to continue circulating.

The notebook becomes a terrific place for jokes, poems, stories and the correspondence between the students and their favorite author.  The notebook serves an even more important role when Mrs. Penrose's baby comes too soon, and she is replaced by a no-nonsense substitute. The students begin to express their fears for their teacher, their frustrations and their hopes.