Millions of children in the ex-Soviet bloc have suffered a "catastrophic decline" in access to education since communism collapsed, the UN has warned.
Poorer families have less access to education, the report says
More than 14m children in the region reach adulthood each year with little or no formal schooling, a report by the UN children's fund (Unicef) says.
Education policy in many countries is inadequate and can reinforce social and economic divisions, it says.
Georgia, Tajikistan and Moldova are among the worst-affected nations.
Much of Central Asia and eastern and Central Europe had attained universal access to education under communism, Unicef said.
But despite the transition to democracy, economic growth and an increase in education spending in many countries, access to education has fallen, the report said.
Some 12m youngsters do not make it to secondary school, and 2.5m do not even attend primary school.
The report, Education for Some More than Others?, found that inequality between rich and poor families was particularly marked.
Co-author Phillipe Testot-Ferry said: "Families with higher incomes get disproportionate access to pre-school.
"[They] ensure good basic education for their children [and] hire the best private tutors, all paving the way to higher education and better jobs."
In contrast, children from poorer families tended to stay away from school or drop out early because they did not expect to reap the benefits of a good education.
Racial inequality was also a problem in countries including Bulgaria, Hungary and Romania, where a large proportion of Roma (Gypsy) children received no schooling at all.
Unicef regional director Maria Calivis called the area's progress a "story of increased disparities".
She said the problem would "undermine the capacity of governments to develop globally competitive economies based on skilled labour rather than cheap labour".
Unicef found that in the region's poorest countries - Armenia, Georgia, Kyrgyzstan, Moldova and Tajikistan - less than 50% of children were in secondary education.
And the report warned that the former Soviet republics of Georgia, Moldova and Tajikistan are not on track to achieve the Millennium Development Goal that all children are able to complete primary school by 2015.
The report, which also covered Turkey, called for an increase in education spending to at least 6% of their Gross Domestic Product - the regional average is currently about 3%.