The group is made up of 27 students, three teachers and nine family members, the state government said in a statement.
A student who died during the attack is named Benjamin Habila.
Abubakar Sani Bello, Governor of Niger according to its chief press secretary Mary Noel Barje, all residences in the area closed and sent the army to rescue the kidnappers from the school.
President Buhari condemned the abduction of the school children.
“The president has instructed the army and police to ensure the immediate and safe return of all the detainees,” Buhari spokesperson Garba Shehu said in a statement on Wednesday.
“The president also sent a team of security chiefs to Minna, Nigeria, to coordinate the rescue operation and meet with government officials, community leaders, as well as parents and college staff.”
A former Nigerian senator, Shehu Sani, told CNN that the school had no perimeter and that militants would have easy access.
Sani, who was also a student at the school, told CNN: “The city is the center of the uprising in the state of Niger. Fulani bandits work within the ashes and there are thousands of people displaced in this area. The bandits in northwestern Nigeria are becoming more deadly and destructive than Boko Haram. ‘
Buhari has recently retired all the heads of Nigeria’s security forces and appointed new people amid growing insecurity and kidnappings in the country.
“The security situation in Nigeria is ‘overwhelming and threatens the peace of the country,’ Sani told CNN.
“It is a pity that the service heads have been allowed for so long,” he added.