Pepe Nietnagel and his fellow students of the Mommsen school come up with all kinds of ideas to get out of doing any actual school work. This includes simulating suicides, setting off the air-raid sirens and abusing the school director's new broadcasting system. They succeed in sending their teacher to a sanatorium and get a replacement that turns out to not be so bad after all.

Pepe Notnagel (who inexplicably had his name changed from the first movie's Nietnagel) and his classmates scheme to get around doing any actual school work by cheating or sending their teachers to the sanatorium. A Swiss documentary film maker disguises himself as his brother in law, who got a position as an exchange teacher, to aid his project of making a movie about the current youth.

Pepe Nietnagel's father has a valuable stamp collection stolen in Amsterdam. Street musician Pit recovers it. To show his gratitude, Pit is invited to Baden Baden and enters the Mommsen Gymnasium. There, he joins Pepe in his pranks.

Due to a plot by the teaching staff, headmaster Taft is forced into early retirement and Knörz is appointed headmaster. However, they didn't count on class 13a, and especially not on their spokesperson Pepe Nietnagel. They are anything but happy about losing Taft, their favorite enemy. Without further ado, Pepe and his friends join forces with Taft and hatch a series of daring pranks to get back at Knörz.

Things may not be fast at the German post office, but they're a lot of fun: postal supervisor Max Sparwein knows a thing or two about it, because he really can't complain about boring and monotonous service on his tour through the city. This is also the experience of journalist Mara Schönwetter, who accompanies him on his walks up and down the stairs to write a report.

Principal Gottlieb Taft's twin brother Gotthold Taft partakes in the most recent prank by faking his death and promising a large inheritance to the Mommsen-Gymnasium and the principal. Of course, the inheritance is tied to many embarrassing conditions.

An orchestra assembles for a rehearsal in an ancient chapel under the inquisitive eyes of a TV documentary crew, but an uprising breaks out.

On the last day of school, teachers and students have only one thing on their minds: finally, vacation. Corinna, the daughter of a prefabricated house manufacturer, has failed to pass her exams despite all her father's attempts to bribe her. With a little trick, her classmates want to fulfill the greatest dream of Corinna's teacher, Dr. Markus. A quick spin of the wheel of fortune and he has won a prefabricated house in a competition. Everything seems to be going well, but suddenly the deception is revealed.