ArtsAlive.ca is an engaging educational website produced by the National Arts Centre in Ottawa and dedicated to teaching students all about the performing arts in Canada. It has a ton of great information on music, French/English theatre, and dance, and the performances held at the NAC since it opened its doors in 1969.
There are a few great collections to help teach about the history of performing arts in Canada:
NACmusicbox.ca features 200 archival recordings of the NAC Orchestra, including 80 original Canadian compositions. The collection is accompanied by contextual essays relating to the history of music, composer biographies, and original program notes.
Imagined Spaces is a really neat collection of set maquettes, which are 3D scale models of theatre sets. Because sets are so hard to store and reuse, maquettes are an important primary source for the history of theatre and scenic design.
The Secret Life of Costumes is an online exhibit featuring NAC's costume collection. The collection has a search database, and suggested activities for incorporating costuming into the classroom.
Persuading Presence is the NAC's online poster archive and exhibit. You'll find a great collection of theatre, dance, and concert posters, as well as background information and activities for the classroom.