After the War shortage of space meant that the whole school, which by this date numbered over 700 boys, never succeeded in getting back into Regent Street, and part of it was housed in the Pulteney School building in Peter Street (just off Wardour Street). Schoolboys returned to the main Regent Street building for assemblies on Monday mornings, swimming and gym, and for art, chemistry and physics classes (on the 3rd floor). The Portland Hall, in Little Titchfield Street, was used for school concerts and speech days. The problems of space, plus the coming of the 1944 Education Act, meant change was inevitable and discussions began which eventually led to the transfer of governance of the school from the Polytechnic to the London County Council. As part of the transfer, the school was renamed The Quintin School and in 1956, it relocated to St Johns Wood. In 1969, the school merged with its neighbour, Kynaston Technical School, becoming the Quintin Kynaston School.
In 2001 the school became a Specialist Technology College and in November 2011, it became an academy. It is now called the Harris Academy St John’s Wood.