AMMAN — More than three million children across Iraq, Lebanon, Iran and Yemen have not set foot inside a functioning classroom in more than a month, the United Nations Children’s Fund said Wednesday, warning that the war’s youngest casualties were being measured not in fatalities but in interrupted brain development, lost literacy and a deepening protection crisis for girls in particular.

In a 38-page situation report released simultaneously from Amman and Geneva, UNICEF said school closures, the conversion of an estimated 1,840 school buildings into temporary shelters for the displaced, the destruction or damage of at least 217 schools by strikes and the collapse of teacher payroll systems in three of the affected countries had combined to produce what its regional director, Adele Khodr, called “the largest single-quarter education emergency the Middle East has seen since 2015.”

“A child who loses a school year does not lose a school year,” Khodr told reporters at a briefing in Amman. “She loses an arc. She loses the friend group that holds her, the routine that calms her, the meal that feeds her, the teacher who notices the bruise. We are running out of time to keep that arc intact, and the next two weeks will decide whether we can.”

The agency put the number of school-age children with no access to classroom learning at 3.14 million as of Monday — 1.42 million in Iraq, 612,000 in Lebanon, 760,000 in Iran and 348,000 in Yemen’s worst-affected northwestern governorates. The figure does not include children whose classes had moved to intermittent online sessions or to shortened tent-school rotations in displacement sites, which UNICEF counted separately as “disrupted but ongoing.”

In Iraq, where displacement from Anbar, Erbil and the Tigris valley accelerated after late-March strikes around U.S. air bases, the Ministry of Education in Baghdad has suspended in-person instruction across seven governorates and shifted to a patchwork of recorded lessons distributed via state television and a messaging-app channel. Education Minister Hala Al-Bayati said in a statement Tuesday that her ministry had identified 9,200 displaced teachers who could be redeployed to host communities, but that fuel shortages, school-building occupations and irregular payroll had stalled the effort.

“We have teachers willing to teach. We have children willing to learn. We have rooms that, for the moment, are full of mattresses,” Al-Bayati said. “The arithmetic is not impossible. It is unfunded.”

In Lebanon, the picture has been sharpened by the resumption of cross-border exchanges with Hezbollah in February and by the sheer compression of geography. UNICEF country representative Edouard Beigbeder said that of the 612,000 Lebanese school-age children currently out of class, roughly 188,000 were displaced from the south and Bekaa to Beirut, Tripoli and the Mount Lebanon governorate, where reception schools were operating at 142 percent of pre-war capacity. Three reception schools in Beirut’s Achrafieh district, he said, were running three shifts a day, with Lebanese children in the morning, displaced Lebanese in the afternoon, and Syrian and Palestinian refugee children — already in a parallel double-shift system before the war — squeezed into truncated evening sessions.

“We are no longer talking about a second shift. We are talking about a fourth shift,” Beigbeder said in a telephone interview from Beirut. “There is a girl in Hamra who is in school from 5:30 to 7:15 in the evening. That is not school. That is the memory of school.”

The Iranian case has been complicated by the wider civilian-supply crisis documented last week by international aid groups, who warned that hospital rationing and rolling blackouts were producing a cascading humanitarian failure inside the country. Iranian state media reported Tuesday that the Education Ministry in Tehran had extended a nationwide suspension of in-person classes through April 30 and had asked teachers to “maintain contact” with students by phone where possible. A WHO field assessment circulated quietly among donor governments and obtained by MetaCurrents estimated that more than 60 percent of primary-school-age children inside Iran had received no structured instruction since March 18.

“The state has not had the bandwidth, and the families have not had the bandwidth,” said Soroush Mehrian, an Iranian-Canadian education researcher at the University of Toronto who has been gathering testimony from teachers inside Iran through a diaspora network. “When the lights are off six hours a day and the bakery line is two hours long, the math homework does not get done. The first generation that learns this lesson learns it for life.”

The protection dimension was singled out by UNICEF as the most alarming and the least visible. In camps and host communities across Iraq, Lebanon and Yemen, the agency said it had registered a 28 percent month-on-month increase in reports of child marriage, a 41 percent increase in reports of child labor, and a sharp uptick in the recruitment of adolescent boys by armed groups in Yemen’s Saada governorate. Girls in particular, the report said, had been pulled out of any remaining learning channels first, often to take on caregiving roles for younger siblings or grandparents.

“Education is not a luxury at the end of the humanitarian list,” said Yasmine Sherif, executive director of Education Cannot Wait, the UN’s global fund for education in emergencies, who was in Amman for the launch. “It is the thing that keeps a girl out of a marriage she did not consent to. It is the thing that keeps a boy out of an armed group. When it goes, everything else gets harder.”

UNICEF said it would launch a $640 million emergency appeal for education and child protection across the four countries, with the bulk of funds directed toward temporary learning spaces, accelerated learning programs for older children at risk of dropping out permanently, cash transfers conditioned on school enrollment, and psychosocial support for both children and teachers. Roughly 90 percent of the requested funds, the agency said, were not yet pledged.

In Doha, Qatari education officials confirmed that an offer first floated late last month to host a regional teacher-recertification and curriculum-coordination hub had been formally accepted by Iraq and Lebanon and was under consideration in Tehran. The hub, to be co-funded by the Qatar Fund for Development and the EU, would aim to keep displaced teachers on payroll and licensed across borders, a measure aid officials said would matter more in 12 months than in 12 days but was being set up now because it could not be set up later.

At the Zaatari camp in northern Jordan, where Syrian refugee families have absorbed new arrivals from southern Lebanon over the past three weeks, headmistress Reem Al-Khateeb said her school’s seventh-grade English classroom had been reorganized to seat 56 children at desks built for 32. Three of the children, she said, had arrived in early March without their parents and had been placed with an aunt who herself had three children.

“The first thing they ask is when school will be over,” Al-Khateeb said. “The second thing they ask is when school will be tomorrow. They want both. That is the answer to whether this matters.”

UNICEF officials said an updated assessment, including a first national survey of learning loss inside Lebanon, would be released alongside the formal appeal launch in New York on April 14.