At 40:20, an advertisement is seen at the back of the makeshift classroom for Swanson's 3.2 Beer, a bygone brand of reduced-alcohol beer. During the Depression, 3.2 beer was a popular choice for "dry" counties that continued to ban full-strength alcohol after the repeal of Prohibition in December 1933.
After Mr. Bascomb storms into the classroom and writes"repent" across the blackboard, the writing changes during his ensuing argument with Miss Hunter. In particular, the second "e" in "repent" goes from large to much smaller.