The report, titled "Free, Quality Education For Every Afghan Child," warns that the failure to deliver international aid is leaving millions of children without hope of education.
The group urges "rich countries" to invest more than $700 million to rebuild schools and supply textbooks over the next five years.
The report's release is timed to come ahead of a NATO summit in Latvia at which member states are expected to assess security and reconstruction efforts in Afghanistan, where the alliance has more than 30,000 troops under its International Security Assistance Force (ISAF).
Oxfam calls education of Afghan children "crucial in improving their lives and in the rebuilding and development of the country."
The report says there has been a fivefold increase in schools enrollment since 2001, to some 5 million children.
But it warns that "poverty, crippling fees and huge distances to the nearest schools prevent parents from sending their children to school."
Thousands more go to classes in tents or crumbling buildings, and have few teachers or textbooks, Oxfam says.
The report cites a particularly acute problem among girls.
"Girls are particularly losing out with just one in five girls in primary education and one in 20 going to secondary school," Oxfam says in a statement accompanying the report's release.
The report also warns of a desperate shortage of trained teachers, low morale among qualified educators, and a problem of "ghost" teachers who collect salaries for work they have not done.