Rathmore began as a stately home, built by Belfast businessman Victor Coates for his family, but the house was passed to the local Bishop who in turn sold it to the Religious of the Sacred Heart of Mary. The RSHM used the house as a convent, where they began a school for girls. Sometime later, a major development project surrounded the convent with school buildings. More recently, a new school building was designed by a past pupil of the school. The new building was completed in time for the school year beginning September 2005. This project included the restoration of the convent, which now houses History, Politics and Religious Education.
Academics
In 2014, it was awarded the Sunday Times School of the Year award. It was the first year that the school had entered the competition. in 2019 the school was ranked 10th out of 159 secondary schools in Northern Ireland with 89.0% of its A-level students who sat the exams in 2017/18 being awarded three A*-C grades. In 2018 it was ranked 20th in Northern Ireland for its GCSE performance with 98.3% of its entrants receiving five or more GCSEs at grades A* to C, including the core subjects English and Maths.
Sports
Rathmore has a history in Gaelic games, winning the All-Ireland senior C title in 2006/7. Within Ulster, Rathmore has competed in the McLarnon Cup in Gaelic football and the Casement Cup in hurling, winning both in 2008 and 2012 respectively. In 2010, Rathmore 4th years won the Leopold Cup in hurling, defeating Belfast neighbors St. Malachy's in the final. They have also tasted success in basketball with the u16 boys winning the Northern Ireland Cup in 2012 and finishing 2nd place the previous year. And recently with football Winning the Lisburn cup, the league and the Belfast cup with the 4th years doing this in 2016.
Recent events
In September 2007, Rathmore closed its Amnesty International branch in response to a change in Amnesty International's policy on abortion. In April 2010, the school debating team won the Northern Ireland Schools Debating Championship, defeating the team from the Royal Belfast Academical Institution in the final at Stormont. It was the first time a team from the school had reached the final of the competition. They spoke in Opposition to the motion 'This House Would Welcome Being Part of a European Federal State'. In 2012, another debating team progressed to the semi-finals, with Brendan nominated for the competition's Best Speaker award. Christopher was nominated the following year and was placed runner up. In March 2013, Rathmore hosted a world record attempt for the most people simultaneously wearing paper hats. This was held in connection with the school's annual Trócaire campaign.
