ISLAMABAD (AFP) - Pakistans flood crisis has damaged more than 10,000 schools, affecting several million pupils and requiring massive investment in a nation struggling with literacy, the UN warned Wednesday. Five to six percent of all schools have been damaged by the floods. This means that between 1.5 to 2.5 million students have been affected, Umar Amal, an official with UNESCO, told a news conference. That number can rise and it will rise, he said, unable to estimate how much it would cost to repair the damaged infrastructure. The United Nations has issued a record two-billion-dollar appeal to cope the disaster, which UN agencies say affected 21 million people and left 12 million in need of emergency food aid. Amal said more than 9,780 government schools were damaged - 2,700 fully and 7,000 partially. The number of private schools affected - a statistic he said was not yet available - would push the figure beyond 10,000, he said. The UN Childrens Fund has said over 10 million children have been affected by the flooding, including 2.8 million under five-year-olds. Education standards are poor in much of Pakistan, particularly in the most impoverished, rural areas worst hit by the floods. Primary school enrolment is around 57 percent and government expenditure on education accounts for just 2.1 percent of Gross Domestic Product. The overall adult literacy rate is 57 percent and Pakistan has three years to meet a Millennium Development Goal target of 88 percent. But many of the flood-affected areas have far worse rates - for example in rural parts of Balochistan female literacy can be as low as seven percent, Amal said. Already before the floods, they were lagging behind... If 9,000 schools are partially damaged and 2,000 schools fully damaged you need a huge investment in education to re-activate it, he warned. The UN Office for the Coordination of Humanitarian Affairs said a further 5,563 schools are still being used to shelter about 567,000 people displaced in the crisis.