Each year, the school conducts the senior and junior one act play festivals. The students from grade IV-X take part in this.

Students become members of the junior, inter and senior G.K. Clubs according to their classes.

As a co-curriculum activity, debating is offered to the students of Grade VI and above during and after class hours.

A National Cadet Corps unit has been functioning at St. Mary’s English School since January, 1980. The cadets are entirely from grades VIII to X. The Air Wing NCC was raised in 1980 at St. Mary’s English School, in which fifty cadets were enrolled in the first year. This was troop no. 15 of no. 1 Bihar Air Squadron NCC, Patna. From 1981 onwards, St. Mary’s English School Air Wing Cadets have been representing at the Gandhi Maidan Ceremonial Parades like the Republic Day, the Independence Day and the NCC Day. Apart from the regular activities, cadets take part in the ATC and CATC at Air Force Station, Bihta (Patna) or at the Homeguard Training Centre, Anandapur, West Bengal.

The Leadership Training for Service and Young Christian Students are two active movements of the school. The LTS is meant for all senior students and the YCS for the Christian students. The members try their best to live up to their motto: “For God and Country” and work for the uplift of society.

The Tarumitra is a students forum for environment.

The Society for the Promotion of Indian Classical Music and Culture among Youth (SPIC MACAY) holds weekly meetings in the campus and invites interested students to take part in their activities.

Xavier’s Cricket Academy (XCA) is a cricket academy of St. Mary’s English School High School, Patna in association with Amikar Dayal Centre for Cricket Excellence. XCA is managed by former cricket captain of India’s Under-19 team, Amikar Dayal.[18] This academy is state’s first professional cricket training academy at school level.