The recess bell rings at the Akha elementary school in Mosul and children come thundering out of the classroom. It's the first day of school.An ordinary scene, except it hasn't happened for three years in this city. Iraqi forces drove ISIS fighters out of Mosul earlier this year in a battle that destroyed huge parts of the northern city, including hundreds of schools."None of us went to school when ISIS was here — we stayed at home," says Ali, who is in sixth grade. "It feels good to be back."ISIS sent government teachers home and ran its own schools — focused on religion and weapons training. Even basic math had a militaristic twist, using the image of bullets to teach children to count.To make up for the lost years, the Iraqi government implemented a system where children could take makeup classes and then sit for exams. If they passed, they moved into the grades they would have been in if school hadn't been interrupted. Junior high and high school students were still sitting for exams while the elementary schools reopened at the beginning of October.'We want to free the children's minds'Iraq is struggling with the aftermath of ISIS, which took over huge swaths of territory when it came in in 2014. There is a shortage of almost everything in the schools.In the classrooms, boys with scrubbed faces and clip-on ties sit at battered desks. Little girls wearing new shoes and jeweled headbands and ribbons in their hair line up against dirty walls covered in graffiti."This is our library," art teacher Ahmed Abdul Aziz al-Jabouri says proudly. He points to an old bookshelf with a few dozen cartoon paperbacks. He says the teachers donated whatever books they had at home."In the future," he says, "we are going to ask students' families to bring books so this small library will grow."Jabouri says each student has been asked to bring a flower to plant in the dirt yard at the school entrance. Decorative fountains made of painted clay pots and homemade benches line what teachers hope will be a flourishing flower garden."Three years out of school is a long time, so it has affected their minds with all the pressure and the bad treatment. We want to free the children's minds from all those bad thoughts," Jabouri says.'Beginning from zero'The battle by U.S.-backed Iraqi troops to drive ISIS out of Mosul destroyed most of the schools on the west side of the city and damaged others on the east.At the education ministry, parents crowd into hallways with charred, blackened walls and wires hanging from the ceiling. Thousands of families who lost birth certificates and other documents when they fled the city are still trying to register their children in school.Even in towns that suffered relatively little damage, some schools haven't managed to open yet.Samira Abdul Satar, the principal of a girls' school in the town of Bartella, was sitting in the director of education's office on the day when classes at her school should have started."We don't have running water," she says. "It's a big school and there are no cleaners. We need the municipality or someone else to come and clean it, at least, and to bring desks to begin with."Ministry officials in the Ninevah school district said they didn't have approval to be quoted. But unofficially, one said: "We are beginning from zero. We don't have books, we don't have pencils, we don't have anything."In one girls' school in east Mosul where classes had started, half of a hallway wall had been blasted out by a rocket-propelled grenade. A classroom next to it was still in ruins.A caretaker at the school said two or three ISIS teachers had taught a few dozen children from ISIS families there. Because the ISIS interpretation of Islam forbids depicting human or animal figures, the group defaced cartoon characters that had been painted on the walls. On one wall, a black smear of paint obscured the features of SpongeBob SquarePants. On another, the faces of elves and Aladdin were painted over.'We want you to succeed'At the Akha elementary school, Principal Yassar Ghanam Shaker lines up the children in the courtyard. In many parts of Iraq, because of overcrowding, students go to school just four hours a day. The boys are the afternoon shift on this day, with a few girls interspersed. Wearing new-looking dresses and their hair held back with white headbands, they primly hold little purses."Make sure you're on time," Shaker tells them sternly. "I don't want any absences. We want you to succeed. "ISIS used this school as a military base, firing rocket-propelled grenades and mortars at nearby Iraqi forces. During the summer, teachers donated paint and came in on their own time to cover the shrapnel holes with cheerful scenes of Mosul.One of the shiny new murals depicts the centuries-old leaning minaret, al-Hadba, a quirky and beloved symbol of Mosul. ISIS blew up the minaret and the mosque next to it as its forces retreated.Shaker, who describes himself as "100 percent from Mosul" pauses and chokes up a bit when asked about the lost monument."Of course it's historic, but Mosul isn't about monuments," he says. "If al-Hadba falls, God willing we won't fall. If our monuments fall, we will still be here." Copyright 2017 NPR. To see more, visit http://www.npr.org/.