The story begins in ‘Black ‘47’ with the arrival of Brother Vincent Culkin to Marybourage as Portlaoise was then called. As famine ravaged the land and poverty was widespread, the Brothers set about uplifting a down throdden and depressed people through education and gave hope for a brighter future.

Portlaoise was the second establishment of the Christian Brothers outside Dublin. Like all such beginnings when the schools were opened on Tower Hill the first classrooms had the minimum of furniture but were filled to capacity with boys anxious for knowledge.This early foundation was marked by a plaque over which stood a statue of Our Lady – Patroness of the schools.

A new school was built fronting Tower Hill in 1906 and opened on January 7th, 1907. Since then many pupils have passed through its doors and St. Mary’s C. B. S. has established a high reputation academically and on the sports field.

Some have achieved distinction, notably Colonel James Fitzmaurice who successfully co-piloted the first East to West Atlantic crossing; Kevin and Thomas O’Higgins who became eminent Statesmen; and Joseph Meehan one of the best-known sportsmen at the beginning of the Century to mention just a few.

Bunting papal flags spanned the streets of Portlaoise during the C.B.S. Century Celebrations in 1947. Fr. E. Matthew assisted by Fathers P. Grace, P. Maher and C. Gallagher all past pupils of the schools celebrated High Mass.