A statement from President Bola Tinubu put the remaining being held at 115.
The recently released children were set to undergo medical checks before being reunited with their parents, Niger state Governor Umar Bago said.
Theresa Pamma, a Unicef official, said “we all know that, for being over two weeks in captivity, those children certainly need some help”, including mental health care.
Bago shook hands with some of the children and led them into a hall where an emir and local officials received them.
It was unclear how the students’ release was secured.
Kidnappers unknown
According to a list of the released children, most of those freed are aged between 10 and 17. The school catered for children as young as nursery-school age.
It was unclear who seized the children from their boarding school in the remote rural village of Papiri.
“Our security agencies, working with the governors, must prevent future kidnappings. Our children should no longer be sitting ducks for heartless terrorists,” Tinubu said in a statement.
Though kidnappings for ransom are a common way for criminals and armed groups to make quick cash, a spate of mass abductions in November put an uncomfortable spotlight on Nigeria’s already grim security situation.
The country faces a long-running jihadist insurgency in the northeast, while armed “bandit” gangs attack and loot villages in the northwest.
In November, assailants across the country kidnapped two dozen Muslim schoolgirls, 38 church worshippers and a bride and her bridesmaids, with farmers, women and children also taken hostage.
The kidnappings came as Nigeria faces a diplomatic offensive from the United States, where President Donald Trump has alleged that there were mass killings of Christians that amounted to a “genocide”.
The Nigerian government and independent analysts reject that framing, which has long been used by the Christian right in the United States and Europe.
The religiously diverse African country of 230 million people is the scene of myriad conflicts that have killed both Christians and Muslims.
Though there was not a breakdown of the kidnapped pupils’ religions, St Mary’s “accommodates Christians and Muslims” as students, Daniel Atori, a spokesman for CAN in Niger state, said.
US Representative Riley Moore, who has seized on accusations of the mistreatment of Christians, said on social media that he met with Nigerian security officials as part of a congressional delegation visit to the country.
The rescue of the 100 children is “a positive demonstration of the government’s increasing response to the security situation”, he said.
– Agence France-Presse