Correct - it changed totally in 1974. Years 11 and 12 had a co-ed classes for 2-3 years beforehand
Kings, Girton and Pembroke are all colleges at Cambridge and the local Pembroke Street sealed the deal for the name.
It was called a School because of the left leaning attitude of the first Headmaster Diana Medlin. She wanted it to be less formal. We lost the school suit, ties and caps for the juniors. There was a general leaning towards the equalisation of the gender that she took far beyond the middle. Some of the ex-Girton teachers struggled with "attitude" of the lads who may not have had their total attention on their lessons. The boys also lost a lot of House sport which we weren't happy about. It is far more equal now.
A lot of Kings lads didn't enjoy the change because we lost our unique identity, history and strong sporting tradition whilst Medlin seemed determined to maintain the Girton one
Co-education is not for everybody - My son was always going to PAC and there are a few others who send their offspring to a single gender school.
We still have King's lunches.................. and John Moody remains revered amongst the ex Kings boys.