Lviv, Ukraine(CNN) When masked Russian soldiers ransacked Nina's home in northeastern Ukraine at 6 a.m. one day in late April, they were not searching for weapons. Instead, they were looking for her Ukrainian textbooks.
The troops held her husband and daughter at gunpoint, but the 48-year-old told CNN she knew it was her they'd come for. As a school principal, she believes they saw her as the enemy.
"They were searching everywhere, even the drains and outdoor toilet," she explained. "They found schoolbooks and tutorials for Ukrainian language."
Nina is not alone. Ukrainian officials say educators in newly Russian-occupied areas of the country have reported increasing cases of intimidation, threats and pressure to adapt school programs to align with pro-Russian rhetoric.
As the war rips through Ukraine, education has become a victim of the conflict -- and a potential battlefield in the fight for control of the country.
Before Russian troops invaded on February 24, around 4.23 million students were enrolled in schools across the country, according to data compiled by Ukraine's Institute of Educational Analytics, a state agency. Now, millions of school-age children have been internally displaced or forced to flee abroad with their families.
After searching her home, Nina said the soldiers -- who forced her to speak Russian -- "gave me a minute to dress and took me to the school."
Once they arrived, she was ordered to hand over history textbooks and quizzed about the school's curriculum. "They came with demands but were speaking very politely," the educator recalled. "They took a laptop from the safe -- it wasn't even mine; it was the laptop of a primary teacher -- and two history books for eighth grade."
She said her captors put a black hood over her head before bundling her into a vehicle and taking her to another location where her interrogation continued.
"They asked about my attitude to the 'military operation,' they accused me of being too patriotic, too nationalistic," she said. "They asked why I use the Ukrainian language ... why I go to Ukrainian church."
Nina said they wanted her to reopen the school and ensure that the children returned, but she argued that it wasn't safe for students or teachers.
"I don't know how long they held me, I couldn't feel time, I was sitting in this black hood, they took it off only during interrogation," continued Nina, whose last name CNN has withheld for security reasons.
Eventually she was released -- but not before her captors had "emphasized that they know about my son and reminded me that I have a daughter," she said, adding: "I considered it a threat."
Days later -- fearful that the Russian troops would return -- Nina and her family fled.
Nina's experience is not an isolated incident. Reports of threats against educators in newly occupied regions have been steadily growing as the conflict has escalated.
One teacher told CNN that Russian troops had approached the principal of her school and "ordered her to hand over all the schoolbooks of Ukrainian language and history, but the principal refused. Her position was so strict that somehow they didn't put any other pressure ... They left emptyhanded."
Some teachers have been able to resume classes for students online, using virtual classrooms similar to those set up during the coronavirus pandemic. But for others, lessons have ground to a halt as internet services are disrupted and schools near the fighting have been forced to close their doors.
At least 1,570 educational institutions have been destroyed or damaged by shelling since the start of Russia's invasion, Ukraine's President Volodymyr Zelensky said in his nightly address on May 2. The president's claims have not been independently verified by CNN.
Ukraine accused Russia of dropping a bomb on a school in Luhansk region on May 7 where 90 people were taking shelter. Serhiy Hayday, head of the Luhansk regional military administration, said the building was leveled in the strike. Sixty people are feared dead.
The country's Education Ombudsman, Serhii Horbachov, told CNN the government had received more than 100 reports and appeals for help from teachers, parents and students in occupied regions since February.
"The employees of educational institutions who remained in the occupation risk their own lives and health, [and] are subjected to coercion, violence, and pressure," Horbachov said.
"There are known cases of abduction of heads of education authorities and school principals," he added. "Teachers are forced to cooperate and work in schools under the barrel of machine guns."
Further examples of Russian forces trying to eradicate Ukrainian identity in newly occupied areas have been seen in the southern region of Kherson, according to Serhii Khlan, a representative of the regional council, who has repeatedly accused occupying troops of threatening educators in recent weeks.
Khlan said Thursday that Russian forces were raiding villages and launching intensive searches, as well as carrying out a census of those left in some areas. He also claimed the Russians have indicated "they will import teachers from the Crimea because our teachers do not agree to work on Russian programs. Those few teachers that agree to work, we know them personally, and they will be held criminally liable for it."
Khlan had previously warned that principals in the town of Kakhovka were being threatened in late April.
His latest remarks came as a report emerged that a new principal had been installed by "occupiers" at a Kakhovka school after the previous headmaster was reportedly abducted on May 11, according to a local journalist.
Efforts to force the Ukrainian education system to align with Russian school programs mirror similar Russification efforts in areas overtaken by Russian forces and Russian-backed separatists in previous years. Russian President Vladimir Putin -- whose baseless claims of widespread oppression of Ukraine's Russian speakers provided a pretext for Russia's February 24 invasion -- has made clear in his own public statements he does not consider Ukraine a legitimate nation.
Oleh Okhredko is a veteran educator with more than two decades of teaching experience and an analyst at the Almenda Center for Civic Education, an organization initially established in Crimea that monitors education in occupied territories. He told CNN it's a strategy he witnessed after Russia annexed Crimea in 2014.
"Crimea became such an experimental field for Russia. Here they started the militarization of education in general," he explained.
He said Russian propaganda reframing historical events was inserted into Crimea's school program -- something he says has had a hugely detrimental effect on children there.
"Ukraine has been totally withdrawn from the schoolbooks and everything becomes the 'history of Russia,'" Okhredko explained. "Children in occupation are really very much influenced being educated in [a] system which constantly needs to have an enemy. Now the enemies are the United States and Ukraine. And this hostility starts to come out among children in form of aggression."
He added: "Those children who studied at school six to eight years ago -- when they were between 11 and 13 years old -- are now fighting against Ukraine. Citizens of Ukraine unfortunately fight against their country."
For now, many educators in occupied areas of Ukraine are trying to resist Russian attempts to adjust their school syllabus, fearful of the impact any changes could have on their students in the long term.
In Luhansk region, Maria, a math teacher and member of the region's school administration, told CNN its members were given an ultimatum to teach using a Russian program. Maria has been given a pseudonym to protect her identity.
"Of course, we told them we won't do that. And they answered 'We'll see. We have a file for each of you.' It's scary," Maria said, adding that they were later sent Russian schoolbooks by email with the request that they "at least read and then decide, because the program is really nice."
"They tried to persuade us. But we told them, we don't have any internet here and didn't receive anything," she explained.
"They even asked 'What is the difference -- Why is it important to study in Ukrainian or in Russian? You teach math -- it's the same in any language.' I resented that ... and I told them, your education, your papers are not recognized anywhere, children won't be able to go to universities. And they replied: 'Which universities? What for? We need workers and soldiers.'"
As Russia's invasion of Ukraine goes on, Maria remains frightened but hopeful.
"We are afraid that they will take away equipment from the schools, we have a lot of new good things in our school," she said. "We are waiting, desperate for our military to come, we think it will happen soon."