St Mary's Anglican Girls' School offers private schooling for girls from Kindergarden to Year 12, and boarding from Years 6 to 12.
St Mary's campus in Karrinyup is located on 40 acres of land.
In 1999, the school built a performing arts venue, The Lady Wardle Performing Arts Centre, with an auditorium that seats 509 people. Later, an adjoining building, The Lady Treatt Centre for Music and Dance, was built. It contains a dance studio, as well as a number of music classrooms and individual music tuition rooms.
The school grounds also boast The Sir Thomas Wardle Swimming Pool Complex, which includes a 50m heated swimming pool, paddle pool and dive pool, which was refurbished in 2011, as well as two gymnasiums (Dannatt Hall and Hearn Hall). Hearn Hall was largely funded by the Federal Government's Building Education Revolution Primary Schools for the 21st Century Program. In 2012, the school completed construction of a new library complex.
In 2005, the St Mary's Anglican Girls’ School Foundation purchased 100 acres (40 ha) of land in Metricup, which is located in the Margaret River Wine Region, to develop its flagship outdoor education facility, St Mary's at Metricup: The Lady Treatt Centre for Learning and Leadership, which was opened in 2008. The centre is the first of its kind for an all-girls school in Western Australia and was funded by the Foundation, as well as donations from Old Girls, parents and friends of the school.The facilities were designed and constructed in a manner which maximises their environmental sustainability. The property contains two dams, two large pastures, an eco-tent camping area, dormitory accommodation and a cottage.