The last grade of the twelve-year secondary school is attended only by girls. At school, they have turned famous for the mischief they get into but their class-teacher Kotková likes them and watches both their joys and distresses with understanding. The girls' production training takes place in a vast machine-tool factory, where they sometimes have conflicts with the leading master, whom they nickname Grouch. At school, the girls suspect the Czech language teacher Krivka of unjust marking.