In 1926, Casson visited an occupational therapy centre in Bloomingdale Hospital, New York City, whilst on holiday, and decided that the UK needed a similar facility; in the late 1920s, Casson decided to establish one. She borrowed £1000 () from her brother, Lewis, to help set up the occupational therapy centre. Dorset House opened in Clifton, Bristol, in 1929 as a residential centre for women with mental health issues. She expanded Dorset House and on 1 January 1930 the UK's first occupational therapy school, known as Dorset House School opened, and she became medical director herself. The school's course would teach not only the medical subjects such as anatomy and physiology, but also occupational treatments such as weaving, bookbinding, and other crafts, as well as how to organise activities such as country dancing and how these activities applied to occupational therapy. Wonderful ciné films of these activities can be found at the Dorset House archive held by Oxford Brookes University library.