Andy falls in love with his drama teacher while his father invests money with two crooks.
James Willet (Stanley Andrews) and Mark Hansen tell Judge James Hardy (Lewis Stone) his land contains 8% aluminum. Andy Hardy (Mickey Rooney) learns that Polly Benedict (Ann Rutherford) is going out with Lt. Charles Copely (Robert Kent). Marian Hardy (Cecelia Parker) tells her father she wants to earn her own living. Andy is smitten with new dramatics teacher Rose Meredith (Helen Gilbert). Willet and Hansen tell Judge Hardy they want to build an aluminum factory and buy his land. Hardy invests and gets them to hire Marian as secretary at his expense. Andy is writing a play about star-crossed lovers in Tahiti, and Rose Meredith announces his play was selected. James tells his family he is president of a new aluminum corporation. Andy wears a suit and talks in a stuffy manner.
In rehearsal Polly plays a native and Andy a rear admiral, but he refuses to kiss her. Later Andy finds Rose crying, and she warns him when he calls her Rose. Marian tells her father that Willet is gone, and nothing has been done. At the bank James meets Rose Meredith and asks her not to hurt Andy. At the dress rehearsal Andy presents the class gift to Rose. Andy acts with Polly and objects to problems. Andy walks home with Rose, kisses her hand, and asks her to marry; but she puts him off until after the show. Andy tells his father he wants to get a job and quit school so he can marry Rose. Judge Hardy warns him about becoming an adult too soon. James tells his wife Emily (Fay Holden) that he lost money and that of others too.
James Hardy learns that the city needs gravel for roads, and he tells his board the city will buy the land for more than Willet and Hansen took. A full audience watches the play and laughs when the moon goes awry. Rose urges Andy to go on with the third act. Andy sees her kiss Bill and then plays disappointed jealousy. Emily cries because she sees her boy has grown up. Andy is missing, and James calls Polly and Rose. Andy is in her garden, and Rose tells him she is marrying Bill. Rose tells Andy that a man can accept things, and he will know many girls. Andy goes to Polly's party, consoles Stickin' Plaster (Terry Kilburn) about the moon, and calls his father. Andy acts grown up, and Polly kisses him.
Andy learns that mature love is still beyond him but gains emotional experience. Judge Hardy's spring fever is greed, and he loses money to two swindlers. Rose creates dramatics as art and in her life with the naive Andy. Once again common human problems are explored with humor and gentle wisdom.