Habibia high school looks like an abandoned monument to war. Its walls have been blasted and scarred by years of rocket attacks. The rendering is pockmarked with snipers’ bullets.

Parts of the building are roped off to keep people away from falling masonry. Visitors are warned not to wander across the grass, in case there are still unexploded mines under foot.

It is a measure of Afghanistan’s desperation to make up for years of lost education that 3,000 children fill this building six days a week, filing past gaping holes in the corridor walls on their way to class.

“When they drove the Taliban out I came back to school,” said Hussein Sultani, a 21-year-old in Grade 10 (G10), who spent four years as a refugee in Iran.

“But we have no glass in the windows. We have no chairs, no tables, there are no carpets and we sit on the floor.” The story is the same in school after school right across the country.

The education awareness campaign, run by UNICEF in the run-up to the start of school term in March, was more successful than anybody could imagine. Murals and stencils of children running back to school can be seen on walls and buildings across Kabul and the western city of Herat.

UNICEF estimates that more than double the 1.5 million expected turned up to school and the numbers have been rising ever since as thousands of displaced people and refugees return home daily.

As a result pupils spill out of ruined buildings into the hot sunlight. They are scattered under trees, and in many cases huddled in tents, some of them provided by UNICEF, some by other aid organisations.

The definition of a school has been transformed into any space that can be used for learning, whether it is under the arches of a viaduct or a room in an old mosque.

The commitment to learning is unquestionable, but the quality of the learning experienced must be severely compromised when children have nothing to lean on as they write except their knees, or have nothing to read because there are no textbooks.

At Wasi Fateh Khan school, five kilometres outside Herat, 2,200 students are crammed into 10 tents and 13 classrooms.

“We need at least 40 more classrooms,” said principal Ahmad Shah. “Most of the existing classrooms need reconstruction work and some of the roofs have fallen in.

“We don’t have enough drinking water, enough textbooks, or even chairs for the teachers. We have floor mats for the students but that is not good enough.”

A quarter of the roof is missing. At the end of each of four dark corridors, a class is huddled on the floor around a blackboard with corrugated iron blocking out the daylight to prevent pupils having to read into the blinding sun.

Where the stairwell meets the first floor, another group is being taught around a blackboard leaning on the wall.

So far UNICEF has distributed textbooks, stationery and pens for about two-thirds of G1 to G3 pupils right across the country and is rapidly attempting to top up supplies for the unexpectedly high numbers attending school. But there is a massive task ahead to supply the higher grades and money is urgently needed to support the painstaking work of repairing each school.

At one school, where classes are held in arches under a viaduct, the principal told me that three days earlier collapsing masonry had crushed six desks.

Wasi Fateh Khan school was surveyed a fortnight ago and work is due to begin next week. When I drove past an hour after my visit they had moved some of the tents around the back to catch the shade in the afternoon. I saw two large clouds of dust rise as something fell off the broken roof on to one of them.

Ted Wragg, TES Teacher magazine, 19