When Mr. Guareschi informs Holling that he doesn't have to re-take sixth grade Math, Holling doesn't quite know whether he should be happy or sad. Mrs. Baker's response when informed of the situation is encapsulated in one word, 'regrettable.'
The pronouncement presents a humorous moment for us readers; Mrs. Baker's stiff formality in language is well-documented throughout the text. Even her disappointments are couched in a lofty, flawless correctness that often has us sympathizing with Holling. When Holling answers with a colloquial 'I guess' to confirm that he does not attend Hebrew school nor Catechism on Wednesday afternoons, Mrs. Baker's answer is typically pedantic (overly concerned with formality in rules) and humorously so:
Since the mutilation of 'guess' into an intransitive verb is a crime against the language, perhaps you might wish a full sentence to avoid prosecution? Something such as, " I guess that Wednesday afternoons will be busy after all."
Although Mrs. Baker seems unapproachable, her humor, courage, and care for her students is fully exhibited in the story. When her husband is reported to be missing in action in Vietnam, she doesn't burden her students with her grief. Her calm dignity and poise inspires her students with courage and a sense of security during a difficult time in American history. Despite her own worries, she comforts Mrs. Bigio after she (Mrs. Bigio) finds out that her Marine husband has died on a reconnaissance mission in Vietnam.
Mrs. Baker spends time on Wednesday afternoons reading and discussing Shakespearean plays with Holling. When Holling complains that defeat doesn't really help anyone to grow (during a discussion on The Tempest), Mrs. Baker reminds him that astronauts continue to participate in making the mission to the moon a reality despite discouraging setbacks.
Mrs. Baker's good humor is evident after she presents the class with twenty four beautiful cream puffs from Goldman's Best Bakery. When Holling thanks his teacher one Wednesday afternoon for her generosity, he gets a surprisingly cheeky answer:
The quality of mercy is not strained.
So, Mrs. Baker's often austere (strict) formality may testify to her conventional ways and highlight her possibly traditional beliefs about proper conduct for a teacher, but it does not hide her care and love for her students. Her choice of the word 'regrettable' is indicative of the kind of dry humor which makes a book like The Wednesday Wars such an enjoyable experience.