In November 1935 the foundation stone for a new assembly hall, dining room and kitchen was laid by Lady Lansdowne. Using reclaimed stone from the old Calne workhouse which the school had bought in 1934, when completed the building stood proudly above the lower grounds of the school.
One of St Mary’s early school houses had been given the name St Faith. The tradition continued with two further buildings named St Prisca and St Bridget. The headmistress, Marcia Matthews, wanted these three saints associated with the school to be represented in relief work on the face of the new building. However, the architecture of the assembly hall called for four plaques and as the hall would be extensively used for music, St Cecilia, the patron saint of church music, was included.