Boarding St Mary's organises boarding specifically on the criteria of age. Within the seven residential houses girls live with their own age group. This offers the maximum opportunity to establish firm friendships and fellowship across the year group which will last throughout school and beyond. Girls are therefore cared for by Housemistresses who are particularly aware of the needs of their charges' own individual age group.

Junior Boarding

The younger girls sleep in medium sized dormitories in School House, St Prisca's and St Cecilia's. All three of these Houses have a cheerful, supportive and exuberant atmosphere. Each House has a resident Housemistress, assisted by Deputy and/or Assistant Housemistresses and often a Resident Tutor.

Senior Boarding

From the age of fourteen, girls enjoy the privacy and independence of a single room. The Senior Houses are open at all times and each room is equipped with a comfortable study area for use between lessons. This encourages girls to adopt from an early age independent learning skills which will be vital in the future.