Pistolník is a teacher who rules the boys' boarding school of a vocational school with a firm hand. Room No. 135 is Pavel, Tonda, Roman, Slavek and especially Olin, nicknamed Koblih, five classmates who, with extraordinary imagination, drive Pistolník crazy with new and new Canadian pranks. Their recessions are only put to an end by the arrival of a new and young teacher, Kamila, who is not affected by their tried and tested tricks. Despite their seemingly carefree life, each of the boys has his own problems, which gradually surface, and so in the avalanche of funny moments, a serious tone is occasionally heard.