In over 170 participating weekly Ontario newspapers, the following 25-word Network Classified ad appeared during the week of April 14, 2013, sponsored by two individuals.

DO YOU ATTEND, OR PLAN TO ATTEND, A Separate Catholic High School?  Religious programs and courses are not mandatory for anyone.  It’s your choice.  www.myexemption.com

The reason for the exemptions is due to provisions in the Ontario Education Act, starting at section 42(11) but specifically sub-section (13).  The only restriction is one’s location.

http://www.e-laws.gov.on.ca/html/statutes/english/elaws_statutes_90e02_e.htm#BK48

Also see   Exemptions from religion for all in RC high schools