France's official secularism fostered mutual respect and understanding but children should be taught in general terms about the world's great religions, he told teachers in this historic central city.
Secularism has been the cornerstone of state education for more than 100 years after bitter battles between the state and the Roman Catholic church. Conspicuous religious symbols such as Muslim headscarves or large crosses are banned.
"I am convinced that we should not leave the issue of religion at the school door," Sarkozy said in a speech whose text was due to be mailed to every teacher in France.
"The origins of the great religions, their visions of mankind and the world should be studied ... (in the spirit) of a sociological, cultural, historical analysis which would allow a better understanding of the fact of religion," he said.
The president said France's Enlightenment values and the secularism of its schools were the best antidotes to religious confrontation that could lead to a "clash of civilisations", but there remained a place for discussion of religion itself.
Sarkozy has challenged the broad national consensus on secularism of public bodies before. His was a lone voice calling for a revision of a 1905 law separating church and state that would have allowed some state funding for building mosques.
Although he has since dropped any idea of overhauling the secularism law, his government has begun studying possible adjustments that would ease the laws regulating the financing of religious communities and public subsidies they can get.