The international community will meet again a year after the promise was made - with more than half of the 1.7 million Syrian refugee children now in school.
World leaders will meet in Brussels this week to discuss how to support millions of people affected by the Syria conflict.
The co-hosts of the April 5 conference say the talks "will reconfirm existing pledges" and look for other ways to help those inside Syria and in neighbouring countries.
One of the existing pledges is a promise to get every Syrian refugee child into school in Turkey, Lebanon and Jordan.
Just over a year ago, at the Supporting Syria and the Region conference in London, leaders said they would make sure all refugees were back at school during the 2016-17 academic year.
So far more than half of those 1.7 million children are in classrooms and rewriting their futures in pencils and exercise books.
But the rest are not. They are still waiting to go to school.
Fulfilling that pledge must be a top priority for the Brussels conference - co-hosted by the European Union, Germany, Kuwait, Qatar, United Kingdom and United Nations. The co-hosts say they will "assess where the international community stands collectively in fulfilling commitments" made at the London conference in February 2016.
Theirworld's #YouPromised campaign has been pressing for months for the pledge to be kept - and for more transparency around the funding processes.
"There is currently no way of telling how much money has been committed for 2017, if it is being spent efficiently or when and how it will be delivered," said Ben Hewitt, Theirworld's Campaigns and Communications Director.
"This makes it impossible for national governments and partners on the ground to plan effectively or make sure we are seeing efficiencies and value for money in the response.
"As a result of a lack of reporting, there is no coherent strategy to ensure the funding is in place to get every Syrian child into school by the end of this academic year.
"Without the protection of the classroom, these children remain desperately vulnerable to child labour, trafficking and early marriage."
The Brussels conference will be attended by 70 delegations from the international community, UN, major donors, charities and other organisations.
Meanwhile, Lebanon's prime minister has warned his country has reached "breaking point" by hosting more than one million Syrian refugees.
Saad Hariri said his country needs urgent investment.
"This issue has reached a breaking point for us in Lebanon. We want the international community to hear us and understand that Lebanon is facing a crisis," Hariri said.
The prime minister said he would appeal at the Brussels conference for international investment to improve infrastructure, including schools.
Lebanon is home to 488,832 school-age Syrian refugees, of which 202,259 are enrolled in school, according to latest figures from the government in February.