The 26-year-old singer, who took time out from her 'Born This Way' world tour to visit the children, was modestly dressed in a buttoned-up white dress, a report said.
The singing star sported a very 1950's look in a high-necked, collared cream dress, clinched in at the waist with a chunky belt and teamed it up with a towering stiletto shoes.
Gaga even added a neck scarf to the dress, creating one of her most conservative looks to date.
Even the 'Poker Face' hitmaker's hair looked demure -- her blonde mane falling sleek and straight over her shoulders.
The singer, who is on the South African leg of her major world tour, went to town on her make-up however, wearing bright red lipstick and huge, false lashes as she met the young children.
Gaga was happy to meet young fans and raise awareness of key issues in the city. After her visit, the star took to Twitter to rave about the city.
“Johannesburg was so wonderful, I can't really put it into words. I am so happy, I haven't slept yet. Laying in bed dreaming of the next tour,” she posted.