How did miss trunchbull lift Rupert into the air and why did she do it?

Miss Trunchbull lifted Bruce Bogtrotter into the air by grabbing him by the collar and hoisting him up, showcasing her immense strength and authority. She did this as a punishment for his theft of a chocolate cake, intending to intimidate him and assert her dominance over the students. This act exemplifies her cruel and tyrannical nature as the headmistress of Crunchem Hall.