"Too many education systems are falling short", with more than 130 million girls missing out on school around the world, Malala Yousafzai has warned, APA reports citing BBC.
"Their futures are worth fighting for," the education campaigner told a global education summit in London.
She said the recovery from the pandemic had to mean fair access to education.
The Global Partnership for Education summit wants to raise $5bn (£3.6bn) to support education in some of the world's poorest countries.
Hosted by the UK and Kenya, it will raise funds for the next five years, creating an extra 88 million school places and supporting the learning of 175 million children.
The pandemic has exacerbated the problems already facing schools in poorer countries - with warnings that children who were forced out of school because of coronavirus might never return.
The UK has promised £430m and other donor countries will be making pledges - with about $4bn of the total expected to be promised by Thursday, in what is claimed as the biggest ever education fundraising event.
Malala told the summit in London of the importance of investing in education, particularly for girls who don't have opportunities "just because of their gender".
"Too many children around the world - girls in particular - were already out of school before the pandemic," said UK Prime Minister Boris Johnson.
"Enabling them to learn and reach their full potential is the single greatest thing we can do to recover from this crisis," he said, urging the international community to contribute.
However, Mr Johnson has faced criticism, including from some of his own MPs, for pushing ahead with a cut in the UK's overseas aid budget.
The Global Partnership for Education gathers funding from donor countries and then distributes it to boost education in low-income countries, with the aim of improving the health, prosperity and opportunities for deprived communities.
Kenya's cabinet secretary for foreign affairs Raychel Omamo warned of the disruption caused by the pandemic - but said "education is the pathway, the way forward".
But Gabriela Bucher, executive director of Oxfam, questioned the priorities of a world in which billionaires could compete in launching private space rockets while millions of children are unable to go to school.
Opening the event, UK Foreign Secretary Dominic Raab emphasised the value of investing in girls' education as the "engine of progress" - with better-educated mothers improving the health and wellbeing of their families.
Education for girls is the "biggest game-changer", he told the summit.