The deluge, which began in mid-June, damaged or destroyed nearly 27,000 school buildings, UNICEF said, adding that it would likely be weeks, even months before flood waters completely subside. In some places, only rooftops of the school buildings are starting to emerge now, it said, AP reported.
The record-breaking floods — which experts say were worsened by climate change — killed 1,735 people and displaced 33 million across Pakistan, mostly in the hardest-hit provinces of Sindh and Baluchistan.
According to Pakistani officials, 647 children were among those killed by the flooding.
UNICEF's education chief, Robert Jenkins, visited some of the flood survivors on Thursday, and later said it was unclear when the children who are still missing classes would be able to return to school.
“Almost overnight, millions of Pakistan’s children lost family members, homes, safety, and their education, under the most traumatic circumstances,” Jenkins said following the visit.
UNICEF has established more than 500 temporary learning centers in flood-hit districts and provided support and school supplies for teachers and flood victims.
Pakistan has also asked the international community to scale up aid for the country's flood survivors, now threatened by the upcoming winter.
On Wednesday, China announced an additional $68 million in aid to Pakistan, bringing China’s flood assistance to Pakistan to $150 million. The announcement came during Pakistani Prime Minister Shahbaz Sharif’s visit to Beijing.
China has so far been the largest contributor in response to Pakistan floods, followed by Washington, which has given $97 million in aid since June. The World Bank has estimated that the floods caused $40 billion in damages.