Now his (Jesus) parents went to Jerusalem every year at the Feast of the Passover. And when he was twelve years old, they went up according to custom.

And when the feast was ended, as they were returning, the boy Jesus stayed behind in Jerusalem. His parents did not know it, but supposing him to be in the group they went a day's journey, but then they began to search for him among their relatives and acquaintances, and when they did not find him, they returned to Jerusalem, searching for him.

After three days they found him in the temple, sitting among the teachers, listening to them and asking them questions. And all who heard him were amazed at his understanding and his answers. And when his parents saw him, they were astonished.

And his mother said to him, “Son, why have you treated us so? Behold, your father and I have been searching for you in great distress.”
And he said to them, “Why were you looking for me? Did you not know that I must be in my Father's house?”

And they did not understand the saying that he spoke to them. And he went down with them and came to Nazareth and was submissive to them. And his mother treasured up all these things in her heart.

-- Luke 2:41-51 (ESV)

Some argue that this scripture proof that Jesus had divine knowledge from his pre-existence because the teachers were amazed at his answers.

Jesus was "listening and asking question to them", not the other way around. "Everyone who heard him was amazed at his understanding and answers [responses]" (Luke 2:47 NIV)

In our modern schools the teachers usually ask the children a question, and they need to provide an answer to proof that they did their homework. However, this case it was the other way around. Jesus was asking the teachers questions and was listening to their answers, then based on the teacher's answers, Jesus responded to their answers.

The period and verse separation that the translators added between verse 46 and 47 creates the impression that the teachers were only amazed at Jesus' "answers". Some translations starts verse 47 with "And" which means that the message is still part of the previous sentence which suppose that the teacher were amazed at Jesus questions too.

According to NAS Concordance, the Greek word "sunesis" often translated as "understanding" could also mean "cleverness" or "insight". Although not much detail was given, one could assume that by asking insightful questions and engaging in dialogue, Jesus could have challenged the existing interpretations and stimulated deeper reflection among the teachers.

If Jesus was truly already all knowing, then the next verse would not make sense:

And Jesus increased in wisdom and in stature and in favor with God and man. -- Luke 2:52 (ESV)