The International Student Identity Card, or ISIC, is a photo-identification card that identifies the holder as a full-time student. It is the only identification card of this kind that is internationally recognized. It is endorsed and recognized by UNESCO.
In Canada, this card may give you access to discounts and services reserved for students. For example, many museums and other cultural institutions recognize the ISIC and offer discounted or waived entrance fees for card-holders.
The ISIC is issued by the ISIC Association. Check their website for more information on where and how to obtain the card.