Against bitter winter's chill, around 400 primary-school pupils sit on the cold ground to take lessons at a ruined school in Al-Rahabah area on the northern outskirts of Yemen's capital Sanaa.

"We do not have clothing to protect us from cold, but we will continue our education despite the obstacles," Maeen Abdulrab, an eight-year-old pupil of the Yahya Mathkour School, told Xinhua.

Abdulrab, like many other pupils, walks long distance each morning to attend class. Many of these schoolchildren even walk barefoot, as they do not own shoes in extreme poverty.

During the nearly five years of civil war which has destroyed Yemen's education system, 2 million school-aged children in the country were forced out of school, while 3.7 million others are facing this risk because of the non-payment of teachers' salaries, according to the UNICEF.

The students of Yahya Mathkour School have been taking classes outside the crumbling building since the war erupted in late 2014, when Iran-allied Houthi rebels seized Sanaa and forced the Saudi-backed Yemeni government of President Abd-Rabbu Mansour Hadi into exile.

Many schools were bombed in airstrikes or destroyed in the ground clashes. Thousands of students have to study near the shadow of the rickety walls or at the shrapnel-filled courtyards in their schools.

Hassan Mahdi, another student, complained of the conditions of the ruined school and the severe cold he was suffering during the open-air classes.

"We suffer from the cold and we do not have warm clothes," Mahdi said.

There were also no table or chair for the teachers.

"The pupils and teachers both suffer from taking classes in the open air during the winter ... It is very hard times," said the teacher Taha Hussein.

One in five schools in Yemen can no longer be used as a direct result of the conflict, according to a UNICEF statement in September.

"Children out of school face increased risks of all forms of exploitation including being forced to join the fighting, child labour and early marriage," the statement warned.