The discovery of the decomposing body of five-year-old schoolgirl Hanifa Abubakar has triggered shock and outrage across Nigeria, where the hashtag #JusticeForHanifa is trending.
The owner of her school, Abdulmalik Mohammed Tanko, has been arrested and the establishment closed.
He allegedly kidnapped Hanifa in the northern Kano state in December to demand a ransom of $14,600 (£10,800).
Police say he later killed Hanifa after realising she had recognised him.
According to the authorities, Mr Tanko, 34, led officers to the school premises where he had buried the schoolgirl's body in a shallow grave.
Her remains were then exhumed for medical examination and a proper burial by her family.
Mr Tanko has not yet been charged.
Hanifa was allegedly abducted in early December outside an Islamic school that she also attended.
Two other suspects have been arrested, police say.
Speaking in an emotional voice, the girl's father Abubakar Abdussalam told the BBC the family was traumatised. Hanifa's mother is currently in hospital after she collapsed and fainted, he said.
He demanded justice from the authorities.
Kano state commissioner of education Sanusi Sai'du Kiru described the kidnapping as a betrayal of trust.
Nigeria is grappling with a wave of kidnappings for ransom, mostly by armed gangs who frequently target schools for mass abductions of students but the kidnapping of students by school officials is extremely rare.