The Orthodox Christian religion is being made a compulsory school subject in four of Russia's regions.
Orthodox Christianity has enjoyed a boom since the USSR collapsed
Pupils in the Belgorod, Bryansk, Kaluga and Smolensk regions will be taught the basics of Orthodox Christianity.
It will also be included as an optional subject in the school curriculum in 11 other regions across the country.
Supporters say the move will help protect traditional spiritual values in Russia. Critics say it violates the constitution of the secular state.
In the Soviet Union the teaching of religion was strictly outlawed in schools and elsewhere.
Orthodox Christianity is Russia's main religion, but the country's Muslim community makes up more than 10% of the total population. There are 86 regions and republics in the Russian Federation.
Responding to the regions' move, the central educational watchdog body, Rosobraznadzor, said the Church was separate from the state, so the basics of Orthodox Christianity should only be taught as an optional subject.
The introduction of the new subject comes after lawmakers in the 15 regions backed the move.
Russian Education Minister Andrei Fursenko also voiced support, saying "schoolchildren must know the history of religion and religious culture".
He said it was a matter for the regions to decide.
"This year, a textbook on the history of world religions is available for the first time. It pays a lot of attention to Russian Orthodox Christianity," he said.
One of the regions named told the BBC that the lessons planned for its schools would concentrate on history rather than questions of faith, the BBC's James Rodgers reports from Moscow.
Nevertheless Muslim leaders have responded by saying that they will ask for lessons on Islamic culture to be extended.