Mary thought she’d have a quiet life
When they return to Israel, Joseph after having another dream decides it is too risky to live in Jerusalem (where they had been living originally) and he takes the family up to Galilee. They settle in Nazareth where Joseph starts up a carpentry business.
Mary thinks she’ll adapt to a quiet life with her child Jesus. However, as I mentioned elsewhere, Joseph had been married previously and his wife had died. In this first marriage Joseph had four sons and several daughters. These sons were the four brothers of Jesus called James, Joseph, Simon and Judas. Joseph had left them with their grandparents when he went to Egypt with Mary, and in any case the eldest one was aged about 21 and the youngest about 7 at the time. The Judean grandparents now deliver the children back to Joseph. These details may be conjecture, but they make sense of the parts of the story that are told later. The upshot is that the virgin Mary who had one child, now actually had nine children to look after, and several of them teenagers.
Every year the family went to Jerusalem for festivals and participated in the Temple rituals. On one of these occasions Joseph and Mary mislaid Jesus. If you have one only child, you don’t lose him, but when you have nine children and other relatives it is easy to forget one. And so Jesus aged 12 stayed in the Temple to argue with the teachers of the Law. This was not a sin, but just a thing which 12 year olds do; they never realize how much trouble they are going to cause with their parents worried sick about them.
Jesus learnt his father’s trade and became a carpenter. Like all Jewish boys he also studied the Scriptures with the Pharisees in the local synagogue. The Pharisee movement had decentralized Judaism towards local synagogues instead of only having a central Temple for worship. They had made obedience to laws in everyday life their thing along with the reading of Scriptures kept as scrolls in the synagogues.