The association revealed that one of the students was freed on December 28, 2021 and another one on January 1.
The Nigerian Baptist Convention said they were trusting God for the release of the remaining four students.
Police spokesman say the suspects were part of 50 suspected criminals arrested for various offences recently.
CAN said they were expecting and praying the bandits would release the remaining 21 students soon.
Christian association leader in Kaduna, John Hayab, and the police confirmed the release.
Aside from the 15 students released on Sunday, 65 of the abducted students remain in captivity with the bandits.
The group wants the United Nations to launch a rescue plan to help Nigeria put an end to the recurring abductions.
Organisers of the programme said the objective is to allow survivors to pick up their lives after the harrowing experience.
State Commissioner for Education said the state was making arrangements with NECO for the traumatised students to take their exams.
More students are still in captivity.