[3] St Margaret's has eight houses: Chaucer, Bede, Herrick, Kendall, Tennyson, Milton, Spenser and Lawson.

It was during Lyon's time that the School motto, Per Volar Sunata (Born to Fly Upwards), came into being and the middy uniform was introduced.

Under the leadership of Sister Teresa (1918–25) the school grew and the adjoining property, Avoca, was acquired in 1918 to provide extra accommodation.

Sister Teresa introduced the house system, a student representative school council and the Dalton method of education.

After the war, a new assembly hall (Eton Hall), extra classrooms and dormitories in East Wing; a gymnasium; the school chapel; Dalhousie classrooms and a boarders’ recreation block and library were erected.

The school celebrated its 75th anniversary in 1970 with the opening of Toorak and its library, staff room and science laboratories.

In 1977 the sisters took the decision to appoint a lay Headmistress, while still retaining ownership and guidance of the school.

It is supplemented by outdoor facilities at Windsor Park and a rowing centre at Breakfast Creek.

This has a water-polo sized heated swimming pool with two 50m lanes, tennis courts with lights, gymnasium with an oak sprung floor, a strength and conditioning gym, an indoor climbing wall featuring seven belay stations and 76m2 of climbing, a dedicated ergometer room to support rowing and modern health and physical education classrooms.

In 2020, the St Margaret's Year 12 cohort 15.9% (14) of students achieve an ATAR of 99 or above, placing them in the top 1% of the state.