Then why was he referred to as rabbi throughout his career? The Pharisees were the only sect then ordaining rabbis through semikhah, or the laying on of hands.
The word means teacher. We have no evidence than he HAD a teacher of his own, to lay hands on him. That is certainly one point of telling the story of the finding in the temple, that even as a youth he was a sage. In Nazareth, his fellow townsmen were astonished to hear him speaking with such authority, which would not have been the case if he had spent time at the foot of someone like Gamaliel. at his baptism, power descended on him from one high.