Today, he is the newly installed 266th Pontiff
, but 70-some years ago, Pope Francis
(previously Cardinal Jorge Mario Bergoglio) was just a boy with a naughty streak.
Sister Martha Rabino, 71 – head of the Colegio de la Misericordia, a Catholic school in Flores, Buenos Aires, where Pope Francis attended preschool – says she's heard all about his reputation as a boy and gotten to know him as an adult.
"All his life he has remained in touch with us," she tells PEOPLE. "He comes spend the afternoon with us twice a year, when he gets all the nuns together and we have tea, and then we take mass."
"As a boy, he was a little naughty," says Rabino. "Sister Rose had been his teacher and died at age 101. He was very fond of her. He would always visit her … he would love to ask her, 'What was I like as a little boy?' And she would always say, 'You were a devil!' and he would laugh and laugh."
It also sounds like the Pope, now 76, was a good student – perhaps with a penchant for math.
"He used to skip up and down the stairs while learning his two times table," says Rabino, "repeating 'two, four, six, eight' over and over again!"
As for the Pope's life today, his nephew Jorge Vallejos, 37, tells PEOPLE that the Catholic Church's new leader has a family life rooted in tradition. And food.
"When we get together as a family we have big meals. We're an Italian family from the north of Italy so our traditions are strong. We eat a lot of pasta, capelletis, stuffed calamari."
Adds Pope Francis's sister, Maria Elena Bergoglio, 65, "I can tell you that he listens to tango in his office while he works."
"He lives very austerely. He has no car, he rides the bus or the subway, or walks."