Mr Okeh was handed the sentence on Wednesday. Before his arrest, arraignment, conviction and sentencing, he was a music teacher and counsellor at Lachez O International School in Agege.
The state counsel said Mr Olabisi sexually assaulted his victim by penetrating her vagina with a finger.
According to the judge, the minor brilliantly presented the sequence of how the convict defiled her.
Mr Ugachukwu was arraigned on one count charge of defilement.
The Ikeja Domestic Violence and Sexual Offences Court has sentenced a man, Isiaka Adeoye, to life imprisonment for defiling a 17-year-old on a farm.
