What did trunchbull do to the boy that could not spell what?

In Roald Dahl's "Matilda," Miss Trunchbull punishes a boy named Bruce Bogtrotter, who struggles with spelling, by making him stand in front of the class and spell "what." When he fails to do so correctly, she humiliates him further by forcing him to eat an enormous chocolate cake as a form of punishment, showcasing her cruel and tyrannical nature as headmistress. This incident highlights Trunchbull's harsh treatment of students and her lack of understanding and compassion.