How old was Mikey grow in The Goonies?

In "The Goonies," Mikey Walsh, played by Sean Astin, is portrayed as being 12 years old. The film, released in 1985, follows Mikey and his friends as they embark on an adventure to find a pirate's treasure. His character is often seen as the leader of the group, showcasing bravery and determination throughout their journey.