Rugby started in St.Mary’s in 2010 with the introduction of tag rugby into PE classes by Patsy Gorman the Leinster Community Rugby Officer for the Midlands region. Interest in the sport really started to grow so by 2013 the school began arranging friendly games against local schools such as Wilson’s Hospital Mullingar. Rugby was greatly supported by Principal Rob Halford and Tom Reehil in the early years.

St.Mary’s first competitive fixtures came in the 2016/17 with the junior team competing in the Pat Rossiter cup. From there rugby has gone from strength to strength with 1^st year, Junior and Senior teams representing the school all coached by Chris O’ Connor. The first trophy won by the school came in 2019 with the juniors winning the Pat Rossiter cup. In 2021 the Seniors won the Anne McInerney Cup and the following year they  won the Anne McInerney shield. 

Several players have won individual honours also with Paidi Farrell representing Ireland in 7s and 15s at U18 and U19 level. Rory Allen in 2022 and Paidi Gorman and Harry Goulding in 2023 were all selected for Leinster Youths. 

The boys teams are currently coached by Patsy Gorman & Dermot Tierney from Leinster rugby and they are assisted by Brian Geraghty. The Senior and Junior teams usually train on Wednesday mornings at 7.30 and the 1^st year team trains on Thursday during lunch. Rugby is open to players of all experience levels.