In the Novels, In the Old Republic, children of about 3 or 4 were taken from their homes to train as a Jedi. Maybe younger. In A New Hope, Luke was the last hope (hence the name of the first SW movie), for the Jedi Knights and the galaxy as well. Yoda thought he was too old, but he knew he had to do it. Anakin was two old, but not mature enough. Luke was much older but mature so look was the better choice to train. Plus Anakin had to worry about his mother all the time, and someone killing Padme, but you\'ll see that in Episode II. Too Bad Luke never went dark. Then the Yuzhan Vong wouldn\'t enter the galaxy 25 years later and try and kill everyone.