Act I: The first floor of "The Seminary for Little Things That Grow Into Women", Night.

The girls are bidding good night to each other when there is a knock at the front door. Miss Sims, the headmistress, shows three men into her study and plugs up the keyhole. Bab, a "bad girl", begins to tell the girls about a secret she has, but is interrupted by Jane Annie, the school's "good girl" tattletale, who promptly goes to tell Miss Sims what she heard. Bab hastily fills the other girls in on her plan to elope that night with Jack, a soldier. When Jane Annie returns with Miss Sims, Bab pretends her secret was how tired she was, and pretends to go to bed. Miss Sims introduces her guests as the Proctor and his bulldogs, who are at the school to capture a student who is "carrying on a flirtation". With the help of Miss Sims, after the girls retire for the night, the Proctor hides inside the grandfather clock, substituting his face for the clock face, and awaits his prey. Tom, a press (journalism) student from the university, enters through the window. He is another suitor of Bab's and meets with her, but she breaks off their relationship. The Proctor emerges from his hiding place and scares Tom back out the window. A moment later, a note is thrown through the window, and Bab suggests that it is from Miss Sims, who used to be the Proctor's sweetheart. As he departs, Jane Annie comes downstairs and lowers the lights, when Jack enters, in a cloak. He discovers he has addressed the wrong girl and drops the cloak as he runs.

Jane Annie disguises herself in the cloak and pretends to be Jack when Bab comes downstairs with her luggage. Bab faints into her arms, Jane Annie screams, and the whole house is alerted. The press students from the university, who have been following the Proctor to get a story out of him, are near enough to hear the scream, so they join the girls and Miss Sims in finding Bab in Jane Annie's arms, fainted from fright. Miss Sims sends the girls to their rooms (they remain on the balcony instead), and the Proctor enters furiously. The press students ambush him with an interview and they repeatedly misinterpret his statements and his attempted corrections, so he invents a story to avoid scandal. Greg and Sim announce that they caught someone - but he's not the undergraduate they were after. Jack appears, swearing revenge for false arrest, and Miss Sims decides to reward Jane Annie for foiling Bab's elopement. Jane Annie requests the Good Conduct Prize, and Miss Sims agrees. While Miss Sims is getting the prize, Jane Annie reveals that she has the powers of hypnotism, and, now that the Good Conduct Prize is safely hers, she is free to be as bad as she likes and will begin the very next day.

Act II: A golf course attached to the school. An arbour and small waterway visible.

The next day, which is the last day of the semester, Caddie, a young servant, is taking Bab out to the golf course to let her see what she is missing, since she is being punished by not being allowed to play. Jane Annie, in a moment alone with her, tells Bab that she has chosen one of Bab's suitors, Jack, for her lover, although she hasn't told him yet.

On the Golf Course

The girls enter, playing at the hole, and Miss Sims, hypnotised by Jane Annie, decides that some men may be admitted as part of their end-of-semester celebration. To liven things up further, she adds that the girls may assume the character of men. When she's alone with Jane Annie, Miss Sims says that she had the oddest dream of writing several letters that morning, which Caddie delivered. The result of letter one is quickly realised, when the press students arrive in cap and gown. They produce Miss Sims' letter, which she identifies as her writing. When the whiskey and soda arrive (letter number two!), Caddie smells a rat and threatens to tell on Jane Annie if he doesn't get a kiss from her.

The girls meet the press students, and since all the girls have decided to be men, the students become girls to oblige them. Just when the fun begins, the Proctor appears and scares off the real men. The girls continue their deception until the Proctor threatens to gate them all, and the girls drop their caps and gowns. Embarrassed, he fines himself a shilling, which Greg and Sim pay. Jack and the soldiers appear by Miss Sims' invitation, and more letters are revealed, to her annoyance. Jane Annie finds Jack and tells him that he will elope with her, something he'd rather not do. Tom and Jack meet face to face and insult each other's intelligence. They nonetheless prepare to run off together, but discover that Caddie has hidden the key to the boatshed. As they formulate their plan, Bab reconciles with Tom, finding Jack arrogant and too idealistic. The Proctor catches Bab in Tom's arms, but she uses her charms to weaken the Proctor's will. She eventually ties him up with her boa and locks him in the arbour.

Jane Annie hypnotises Caddie

The carriage has arrived to take the lovers away, but they can't cross the river without the boat. Jane Annie hypnotises Caddie, who has hidden the key in an undisclosed location on his person. When he gives up the key, Miss Sims catches them. Jane Annie hypnotizes her into giving her blessing, and then she hypnotizes the Proctor into paying for their expenses. Jack refuses to accompany Jane Annie, so she hypnotizes him as well, and he agrees to love her. The happy couples escape, and when the spell is broken, Miss Sims and the Proctor realise that a joke has been played on them, and their reputations are ruined. The Proctor attempts to get a moral out of it, but since he can't recall it, he suggests "you'd best go home without it". Caddie would suggest that the moral is "no more Good Conduct prizes", but the others don't allow him get a word in on the matter.