Popoola reportedly taught Obasanjo at Baptist Boys High School, Abeokuta.
Our correspondent gathered that the nonagenarian died at his residence in Ilaro, a town in the Yewa South Local Government Area of Ogun State on Thursday.
A member of the extended family, Tope Popoola, said the retired teacher died at about 12 noon Thursday.
The family source said Popoola gave up the ghost a few days after he was discharged from the Federal Medical Centre, Idi-Aba, Abeokuta, where he had been admitted for treatment.
It was gathered that apart from Obasanjo, the late Popoola also taught some other prominent persons in the country, including the Olubara of Ibara, Jacob Omolade; a former Vice-Chancellor of Olabisi Onabanjo University, Prof Saburi Adesanya; and the late historian and politician, Saburi Biobaku.
Obasanjo and Omolade had, late last year, visited Popoola in his Ilaro home.