New school textbooks promoted by the Mexican government have sparked a battle between the leftist president and opponents who have burned them and taken the case to the highest court.
Critics allege that the books promote communism, homosexuality and contain factual errors.
They want the government to refrain from distributing the materials from Monday, when millions of students will start a new school year in the Latin American nation.
One of the most radical protests took place in the southern state of Chiapas, where parents in an Indigenous neighborhood set fire to books they said were the work of "the devil" and taught "communism, homosexuality and lesbianism."
Stimulating the "sexuality of our children with this type of ideology... gives rise to pedophilia," said Jose Tomas Bermudez, a local evangelical pastor.
The president of the conservative opposition National Action Party (PAN), Marko Cortes, called on parents to "destroy (the books) in their entirety."
Speaking against the backdrop of campaigning to choose candidates for the 2024 presidential election, Cortes alleged that the texts seek to "indoctrinate" students.
President Andres Manuel Lopez Obrador, a leftwing populist, has described the row as "politicking" stirred up by conservative opponents.
He frequently attacks what he calls his opponents' "neoliberal" economic model favoring free markets and privatization, and vowed to overturn it when he came to power in 2018.
The Mexican leader criticized a decision by the Supreme Court to suspend the distribution of the books in the northern states of Chihuahua and Coahuila.
"It's medieval," Lopez Obrador said of the book burning, likening it to something "from the Inquisition."
His government says the new materials recognize the country's diversity and put the community at the heart of education.
Authorities in at least eight of Mexico's 32 states have refused to distribute the books.
Although it has granted two injunctions, the Supreme Court has yet to rule on the merits of the matter.
- Thousands march -
In the opposition-governed central state of Aguascalientes, thousands of people marched in protest at what they called "Marxist ideologies" spread by the new books.
Education Minister Leticia Ramirez has defended the new teaching materials, which she said promoted values such as solidarity, honesty, respect and social justice.
The books mark a change from the previous promotion of "individualism, disengagement from the community and rote knowledge," she said in a televised news conference.
Critics point to several factual errors in the books, including the wrong date of birth of Benito Juarez, Mexico's first Indigenous president.
They also allege bias in the content, such as the assertion that "hope was the soul of the campaign" that brought Lopez Obrador to power in 2018, and the allegation that he was the victim of voter fraud in 2006.