Here is the CRA website that discusses the circumstances where amounts paid for "religious instruction" to a religious school might be claimed in whole or in part as a charitable donation. Paragraph 3 of the below document might be applicable to you. If in doubt, you should contact the school and ask them directly as to the tax treatment of the amounts for which they issued you the "religious instruction tax receipt".
http://www.cra-arc.gc.ca/E/pub/tp/ic75-23/ic75-23-e.html