A U.N. report shows than more than half of the world's countries have failed to achieve gender parity in education for girls in primary and secondary schools.

The report released Friday by the U.N.'s cultural agency UNESCO focused on the evolution of education for girls since 2000, when 164 countries agreed on common education goals.

Although 62 million girls are still denied their basic right to an education, the number of out-of-school girls has declined by 52 million in the last 15 years, according to the Paris-based organization.

The number of countries that did reach gender parity in both primary and secondary education has risen from 36 to 62 from 2000 to 2015.