UNICEF says the household mapping conducted in Katsina State indicated that no fewer than 620,000 children were out of school.
The UNICEF State Coordinator, Shehu Mohammad, made this known at the launch of the 2015 Enrolment Drive Campaign in Kankia, Katsina State.
Mohammad, who said that girls recorded 55 per cent out of the number, attributed the development to the negative perception of formal education.
He also hinged the development on the value placed on girl-child education in the northern part of the country.
The coordinator further revealed that a report published in 2012 showed that about 8.7 million of primary school age children were out of school in Nigeria.
He added that 74 per cent of them never entered school while five per cent were classified as dropouts.
Mohammad said UNICEF adopted the enrolment campaign as one of the key intervention initiatives under the Girls Education Project 3.
According to him, the project targets enrolment of additional one million girls in five northern states.
In his remarks, Governor Aminu Masari of Katsina State stressed the importance of girl-child education, pledging that his administration would continue to accord education top priority due to its importance in nation building.
Masari called on people of the state to enrol their children in schools, pointing out that the government had already designed policies to develop the education sector.
Also speaking, the Emir of Katsina, Alhaji Abdulmumini Kabir, called on parents to enrol their children in schools.
The emir directed traditional rulers in the state to continue to partner with other stakeholders to improve the education sector.
He urged district and village heads in the state to embark on inspection visits to schools in their domains.
Kabir, however, lamented the dearth of qualified teachers, saying that the development was affecting the education sector negatively.