By Imogen Foulkes
BBC correspondent in Geneva
The United Nations children's organisation says 115 million children worldwide are missing out on an education - and most of them are girls.
Pakistan has one of the widest gender gaps
The UN wants to achieve gender equality in primary education in 2005, as part of the Millennium Development Goal of universal primary education by 2015.
There is evidence that more children are now going to school, Unicef says.
However, it adds that many countries in South Asia, Africa and the Middle East cannot meet the target this year.
Unicef is especially concerned about the situation in west and central Africa.
It says emergency measures are now needed to promote primary education.
Only five countries out of 24 are set to achieve gender equality there.
Conflicts in Liberia, Sierra Leone and the Democratic Republic of Congo have done incalculable damage to children's education.
Unicef executive director Carol Bellamy said: "Education is about more than just learning. In many countries it's a life-saver, especially where girls are concerned.
"A girl out of school is more likely to fall prey to HIV/Aids and less able to raise a healthy family."
In South Asia, Unicef says, progress has been made, but not enough.
Across the region, 42 million children do not go to school.
Afghanistan and Pakistan have the widest gender gaps.
For Pakistan to have the same number of girls as boys in school by 2015, it would have to increase girls' school attendance by more than 3% each year.
In eastern and central Europe, there is cause for concern too.
The introduction of fees for tuition, schoolbooks and uniforms has led to rising drop-out rates - and girls drop out sooner than boys.
Belarus and Tajikistan will not achieve gender equality, neither will Turkey.
Unicef says a quantum leap is needed to achieve universal primary education by 2015, and insists the effort must be made.
The UN's primary Millennium Development Goal is the eradication of poverty, and education is fundamental to achieving that.