Is it obligatory for parents to teach a Muslim newborn the two Shahadas upon reaching puberty?

The child follows the Muslim parent among his parents. If one or both parents are Muslim, the child is ruled to be Muslim, and there is no need to command him to recite the Shahada upon reaching puberty. However, if both parents are disbelievers, then that is necessary. Imam An-Nawawi said: "Every child is born predisposed to Islam. So, whoever has one or both parents Muslim, remains upon Islam in the rulings of the Afterlife. And if both his parents are disbelievers, the rulings pertaining to them in worldly matters apply to him."