The Athlone outfit secured the win in tough playing conditions on Wednesday.
Marist Athlone have won the first Connacht Schools Senior League title in 12 years on Wednesday.
The win came courtesy of a late try from centre Thomas Cotton against perennial rivals Sligo Grammar School to secure the title on a final scoreline of 17 - 14.
Marist Athlone Sam Fogarty says the conditions played their part in the outcome:
Kevin Egan was at Creggs Rugby Club for the game: