Children's pioneer camp on the coast of Black Sea. On the eve of the war game "The Classified City" - annual and traditional , someone steals the team bugle - a source of pride for the entire squad.

The heroes of the film are students of a pedagogical university, those who, after a year or two, have to carry knowledge to schoolchildren, "to sow the rational, good, eternal." In the meantime, student practice. True, the practice is not quite ordinary, because for the first time students leave far from the walls of their own university, for the first time they meet with students in the classroom not in the presence of their teachers, those with whom life encounters them daily at the institute, but with those who have been working for more than a year at school.

Two completely different sons grow up in the same family. The youngest, Frol Kalitkin, is an exemplary seventh-grader, winner of Olympiads, the first student. And the eldest, Andryusha, is a loafer, a loafer and a dude. The “correct” Frol takes up the upbringing of his brother.

The film is about difficult-to-educate kids and those who are involved in their upbringing.