Complex sentence: She sent a six-year-old boy who allegedly threw a sponge across the dormitory to the headmaster in his pyjamas and dressing gown; the boy was then caned.
Split into simpler sentences: She sent a six-year-old boy, who allegedly had thrown a sponge across the dormitory, to the headmaster. Still in his pyjamas and dressing gown, the boy was then caned.