One of the rewards of helping to track global education over the past decade has been watching progress in getting more girls into school. But as we mark International Women's Day, I'm more conscious than ever that the glass is still not even half full: 31 million girls have never set foot inside a classroom, and half of them are unlikely ever to do so.
In addition, over 100 million young women in low and lower middle income countries are unable to read a single sentence.
That's why the next set of global education goals, for the period after 2015, needs to include special efforts to ensure that all girls and boys - rich and poor, urban and rural - have an equal chance of getting a quality education.
Today we release the gender summary of the 2013/4 EFA Global Monitoring Report - the latest edition of the world's major education survey, which I directed. It shows that the gap in numbers between boys and girls attending primary school has narrowed. But in some poorer countries, many fewer girls than boys go to primary school, and fewer still to lower secondary school.
And just getting into school is far from being sufficient. Children need to complete primary school - and then go on to finish lower secondary, vital years for acquiring job skills. But new analysis for our report shows that in low-income countries, it may be generations before all children are completing primary and lower secondary education.
To give you an idea of the scale of the problem: In sub-Saharan Africa, if recent trends continue, all the richest boys will be completing primary school by 2021, and all the poorest boys by 2069, but the poorest girls will not catch up until 2086 - and it will take until 2111 for all the poorest girls to be finishing lower secondary school.
To escape from this depressing trajectory, we need to focus education policies and practices on the most marginalized, to make sure no one is left behind. That's what equity means, as opposed to equality: equity is about fairness, it's what you have to do to get to equality.
When international education experts drew up the six Education for All goals in 2000, they wrote the language of equity into the goals. So why is equity in education far from being realized, with only two years to go until the deadline for the goals in 2015?
It's vital to resolve this question, because the international education community is now proposing new goals, for the post-2015 period. And once again equity is there in black and white. What can we do to make sure that this time, good intentions translate into real results for the world's marginalized girls?
We not only have to dedicate special efforts and resources to reaching them. We also have to measure how they are doing, using data that are broken down - or disaggregated - group by group, region by region.
Back in 2000, disaggregated data were harder to come by. Now we do have such data, even if they are not perfect. So we should write concrete targets into our new goals. Not just for raising average education levels, but for respecting the right of every person to an education.
Yes, education is a right, not just in a moral sense but in a legal sense, too. Almost every country in the world has signed up to international treaties guaranteeing that right. On top of that, education has remarkable power to boost every other aspect of people's lives - especially education of girls and women, as the 2013/4 EFA Global Monitoring Report shows.
Education reduces women's poverty and boosts their chances of getting jobs that pay as well as men's.
It has enormous benefits for women's health, as well as their children's, saving millions of lives through better knowledge of disease prevention and treatment. Education empowers women to make better life choices, helping to avert early marriage and childbirth
Education is also part of the basic social contract between a government and its citizens. Yet that contract is being broken for millions of girls and young women. Most of them already live on the margins of society. When we make our education pledges for the era after 2015, let's ensure we don't fail them again.
Read the Gender Summary online:bit.ly/18n8OEx
World Education Blog: http://efareport.wordpress.com