There are three months of school left and all of the Peanuts gang are under pressure from too many tests and homework assignments. They now have to make preparations to write a report on a field trip to an art museum.

Charlie Brown's grades are falling from A to C and he has to receive a big grade on his museum report in order to salvage his grades for the entire term. Simultaneously, he must fight off the distraction of Peppermint Patty and newcomer student Marcie, both of whom have feelings for him. Unfortunately, on the way to the art museum, Charlie Brown, his sister Sally, Peppermint Patty, Marcie, and Snoopy inadvertently arrive in a supermarket and mistake it for the art museum. When Linus shows Charlie Brown and Lucy slides that resemble the works he took pictures of, Charlie Brown's hopes of salvaging his grades are shattered. As he waits for his graded report, he expects the worst of it all. However, everything works out for the best, as his teacher assumes his report is a description of an art museum described through the description of a supermarket and she gives him the grade he needs.