The school's origins can be traced back to the closure of two previous Roman Catholic single-sex schools in the area: St. Patrick's (an all-boys school) and Notre Dame (an all-girls school). In 1990 the two were merged into a new school, using the newer buildings of Notre Dame in the
Castlehill neighbourhood on the west side of Dumbarton (completed in 1969). In order to represent both of the previous schools, the new name "Our Lady and St. Patrick's" was chosen. Previously, a local
convent had a large influence in the school as they previously managed the all-girls school Notre Dame, which was incorporated into it. The school colours, green and blue were chosen from the existing schools and are the colours most commonly associated with the namesake religious figures; blue for the
Virgin Mary and green for
St. Patrick. ==21st century==