Turkey's new school curriculum drops Charles Darwin's theory of evolution and adds the concept of jihad as patriotic in spirit.
The move has fuelled fears President Recep Tayyip Erdogan is subverting the republic's secular foundations.
The chairman of a teachers' union has described the changes as a huge step in the wrong direction for Turkey's schools and an attempt to avoid raising "generations who ask questions".
Ismet Yilmaz, the country's education minister, said the controversial decision to exclude the theory of evolution was "because it is above the students' level and not directly relevant."
A member of the opposition Republican People's Party, Mustafa Balbay, said any suggestion the theory was beyond their understanding was an insult to high school students.
"You go and give an 18-year old student the right to elect and be elected, but don't give him the right to learn about the theory of evolution...This is being close minded and ignorant."
The theory of evolution is rejected by both Christian and Muslim creationists, who believe God created the world as described in the Bible and the Koran, making the universe and all living things in six days.
Mr Erdogan, accused by critics of crushing democratic freedoms with tens of thousands of arrests and a clampdown on media since a failed coup last July, has in the past spoken of raising a "pious generation".
The curriculum, effective from the start of the 2017-2018 school year, also obliges Turkey's growing number of "Imam Hatip" religious schools to teach the concept of jihad as patriotic in spirit.
"It is also our duty to fix what has been perceived as wrong. This is why the Islamic law class and basic fundamental religion lectures will include [lessons on] jihad," Mr Yilmaz told reporters. "The real meaning of jihad is loving your nation."
Jihad is often translated as "holy war" in the context of fighters waging war against enemies of Islam; but Muslim scholars stress that it also refers to a personal, spiritual struggle against sin.
Mehhmet Balik, chairman of the Union of Education and Science Workers (Egitim-Is), condemned the new curriculum.
"The new policies that ban the teaching of evolution and requiring all schools to have a prayer room, these actions destroy the principle of secularism and the scientific principles of education," he said.
Under the AKP, which came to power in 2002, the number of "Imam Hatip" religious schools has grown exponentially. Erdogan, who has roots in political Islam, attended one such school.
He has spent his career fighting to bring religion back into public life in constitutionally secular Turkey and has cast himself as the liberator of millions of pious Turks whose rights and welfare were neglected by a secular elite.
Liberal Turks see Mr Erdogan as attempting to roll back the work of Mustafa Kemal Ataturk, the Western-facing founder of modern Turkey who believed education should be free of religious teachings.
Some government critics have said the new curriculum - which was presented for public feedback earlier this year - increased the emphasis on Islamic values at the expense of Ataturk's role.
But Mr Yilmaz said nothing about Ataturk or his accomplishments had been removed. Changes only emphasised core values such as justice, friendship, honesty, love and patriotism.
Mr Balik, the head of the union, said the changes were being made in an attempt to stamp out dissenting ideas.
"The bottom line is: generations who ask questions, that's what the government fears," he said.
Additional reporting by Reuters
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