Another find from the Internet Archive
Table from The public schools of Ottawa (1918) found at http://www.archive.org/details/publicschoolsofo00markuoft
In 1918 First Avenue School had 645 students occupying 13 classrooms plus a kindergarten. Connaught School, new at the time, had 604 students in 13 classrooms plusĀ a kindergarten. Mutchmor had 545 students in 11 classrooms plus a kindergarten for an average of almost 50 students per classroom.

found at http://www.archive.org/details/publicschoolsofo00markuoft