St Mary’s N.S. was established in September 2000 following the amalgamation of St Elizabeth’s Convent N.S. and Mostrim Boys' N.S. It is a Catholic co-educational primary school under the patronage of the Most Reverend Dr Francis Duffy, Bishop of Ardagh and Clonmacnois.

From 2000 until 2003 our school operated on both campuses of St Elizabeth’s N.S. and Mostrim Boys' N.S. In 2003 all pupils and staff moved to what was St Elizabeth’s Convent N.S. At that time there were 189 pupils enrolled in seven mainstream classes. There was a total staff of sixteen comprised of eleven teachers, two special needs assistants, a part-time secretary, a part-time caretaker and a part-time cleaner.

The following years saw unprecedented population growth in Edgeworthstown and consequently the school population increased significantly. In 2007, our school was selected to participate in Delivering Equality of Opportunity in Schools (DEIS) and received DEIS Rural status.

In May 2013 the building of our current school began. Phase One saw the building of the mainstream school which opened in September 2014. Phase Two saw the building of Suaimhneas Mhuire, our special education centre that caters for specific children with autism and is attached to the mainstream school, which opened in September 2015.

On the 15th October 2015, our new building was officially opened by Ms Jan O'Sullivan, Minister for Education and Skills. It was blessed and dedicated by our Patron, Bishop Francis Duffy.

Currently, there are 385 pupils enrolled in twenty-one classes. We have fifteen mainstream classes and six Primary-Age classes in Suaimhneas Mhuire. There is a total staff of sixty comprised of thirty-three teachers, seventeen special needs assistants, a secretary, a caretaker, a cleaner and seven bus escorts.

Our school, which is the only Catholic primary school in the parish of St Mary's, Edgeworthstown, is situated on the outskirts of the town on the Granard Road (N55). It is part of an extensive campus in Edgeworthstown. St Mary’s Childcare Centre is located beside our school and Edgeworthstown Community Centre is located behind both our buildings.