Staff at Salisbury comprehensive say behaviour has improved dramatically since the 1,500-pupil secondary was split into two smaller schools.
The school in Enfield, north London, is based on two sites 10 minutes' walk apart. For decades they were run as an upper and lower school.
Head Martin Rainsford decided last year that drastic change was needed to boost results at the school, where inspectors had found serious weaknesses.
In September the school's two sites became separate 11 to 18 campuses and were named Turin and Nightingale. Each has different teachers, a different head of site and about 750 pupils. Only during PE do pupils from the separate campuses use the same facilities.
Caroline Allen, the associate head who runs Nightingale, said the split has given pupils a greater sense of belonging and helped older students to act as role models for younger children.
"In my first years of teaching at Salisbury I didn't know all the students in one year group, let alone all of them," said Ms Allen.
"In the six months since we set up Nightingale I've got to know the name of every child. We are a real community."
But not all such schemes have been successful. Rhodesway in Bradford split into two 11 to 16 schools and a sixth-form centre n 2002 . But inspectors complained about inconsistency across the campuses, and it was placed in special measures.