Piercy Jackson is good too!
But yea I think Pendragon is age appropriate. It says 10+ https://www.commonsensemedia.org/book-reviews/pendragon-series
There's also Chronicles of Narnia, A Wrinkle in Time (but the main character is a girl, so idk if he would relate, don't bother watching the movie).
I enjoyed His Dark Materials, first book Golden Compass at that age, but this website says 12+ so this is something you can read down the line https://www.commonsensemedia.org/book-reviews/the-golden-compass-his-dark-materials-book-1
