As post-war austerity restrictions on building supplies were eased, the Schools were able to undertake the substantial list of extensions that had been planned. In 1950, the A-E block of classrooms was built at the south side of the Boys’ School yard. In 1955, as part of the 250th anniversary of the Schools, the Girls’ Library was refurbished thanks to the substantial bequest in the will of former pupil, Florence Moat. In honour of her benefaction, it became the Florence Moat Library.

In 1956, the Advanced Chemistry Laboratory was built over the old air raid shelter. The original plans to extend the Girls’ School failed to receive planning permission and consequently further DAGS extensions took place later. The Lecture Theatre, which also served as a music classroom, and new PE changing rooms were built in 1957. Along the eastern side of the quadrangle, the ‘goldfish bowl’ was built for use by Sixth Formers with a biology laboratory above. In the following year further quad infill led to a block with offices and small tutorial rooms and in the Boys’ School a flat-roofed Sixth Form classroom was built in the corner of the yard.