Jesuit-run Loyola High School wants to be allowed to use its own course and teach it from a Catholic perspective.
The law allows for such an exemption where the alternative course is deemed by the minister of education to be equivalent to the provincial program.
The minister turned down the school's request, but the Superior Court of Quebec sided with the school and allowed the exemption.
The provincial appeal court, however, reversed that decision in a ruling last December.
As usual, the Supreme Court gave no reasons for its decision to hear the case.