St. Mary Catholic High School Brockville is a Catholic high school in Brockville, Ontario. The school's current principal is Laura Mackler, with Stephanie Koekkoek as the vice-principal. The school has a gymnasium, library, large guidance and special education departments, five science classrooms, four English classrooms, a construction lab, music room and a stage/drama room. St. Mary also features a "cafitorium" (auditorium that is transformed into a cafeteria). The school day commences at 8:05 am and concludes at 2:08 pm. Unlike the local public schools, St. Mary only has four periods per day.

St. Mary Catholic High School
Address
40 Central Avenue Brockville , Ontario , K6V 1P8 Canada
Coordinates	44°35′59″N 75°41′45″W / 44.59973°N 75.69591°W / 44.59973; -75.69591
Information
School type	"Catholic" high school
Founded	1951
School board	Catholic District School Board of Eastern Ontario
Superintendent	Brent Bovaird
Principal	Laura Mackler
Chaplain	Sean Shallow
Grades	7-12
Enrollment	595 (2019-2020)
Language	English
Area	Brockville
Colour(s)	Blue and White
Team name	St. Mary's Crusaders
Feeder schools	St. John Bosco Catholic School, J.L. Jordon Catholic School, St. Francis Xavier Catholic School, St. Joseph Toledo
Website	stmarychs.cdsbeo.on.ca