Fifth-grader Ottokar is always getting into trouble for trying to fix what he perceives as injustice. He gets revenge on his teacher Mr. Kunz, who gives preferential treatment to girls and humiliates poor students. He fights with his dishonest classmate Pillenheini, who votes against him in the school's Pioneer Council elections. And his efforts to help a drunk tenth grader get home only make the older boy's mother angry.

Although Ottokar's actions generally make him unpopular, his new teacher Mr. Burschelmann recognizes his good intentions and tries to steer the boy's concern for fairness in a more helpful direction by inviting him to join the Pioneer Council at school.