An important landmark in the battle for children’s rights will be marked today by the United Nations Secretary-General and celebrities ranging from Shakira to Lang Lang, all marking the 500-Day point of the #EducationCountdown to reach the Millennium Development Goals of universal education.

In 2000, world leaders declared that by December 2015 every child would be at school. Shocking evidence has just become available which shows 58 million primary-age children are not at school. Another 250 million go to school but leave unable to read. About 500 million school-age girls will never complete their education.

What is angering young education campaigners everywhere is that progress in meeting the goals has only recently stalled, with global education aid cuts and domestic governments failing to honor their promises. Despite significant progress allowing tens of millions of children to enroll into school at the start of the millennium, a recent estimate suggested that at the current rate we must wait until 2086 for the last girl to have a primary education in Africa.

My greatest concern is that the weakest and most vulnerable children stricken by poverty are the ones with the lowest chance of benefiting from our goal of universal education: the street child, child laborer or child bride, the boys and girls in the most remote rural areas and the most marginalized.

Complacency can no longer be the norm as millions of girls and boys lose out on the opportunity to have the most basic right to opportunity. As co-founder of A World at School and the Chair of the Global Business Coalition for Education, I am joining thousands of campaigners from across the globe to make education the number one priority over the next 500 days.

Realising that individual social justice goals are united by the right to education, today partners are uniting from across the globe in the #EducationCountdown. Over 100 organizations have committed to prioritizing education during the next 500 days. The Global Business Coalition for Education is approaching 100 corporate members who agree that education underpins business interests. A Global Faith Coalition has emerged and Youth Ambassadors are mobilizing in nearly 100 countries.

Digital citizens are also taking action in the thousands and slated to reach millions through a universal social media “thunderclap” to be released at 9:30 a.m. EST. Many will realize that today my Twitter account was taken over — not by a hacker but by someone who understands that counting down is what needs to happen. Count von Count has joined the campaign to help draw attention to the 58 million out-of-school children in a unique partnership with Sesame Workshop.

But I know the public is prepared to do much more than tweet and spread the word. Today, we take the appeal global with targets, timetables and demands for results. After a summer in which children have seen their schools bombed in Gaza and when in conflict zones 28 million children are being denied the right to education, we will hold governments to account. All countries must endorse the Lucens Guidelines and protect schools from attack. We must not let innocent children, victims of the Syrian war living in neighboring countries, go without education. The children in Lebanon are still waiting for aid agencies to finance less than $10 per child per week for them to have the chance to learn.

These children have waited too long. Today is the day we start holding world leaders to account.

Join the #EducationCountdown movement at www.aworldatschool.org/educationcountdown.