Sadako said:
^ Same thing goes for the Prequels. Oh hey, look at that, back on topic!
Seriously, though, there are scriptwriting classes and seminars even at community colleges. It's not like it's this lost art, some sort of deep magic that was only known to the druids who used it to build Stonehenge. Learning how to write a decent script is totally possible, even for Lucas and Shyamalan.
Lucas has often said how much he hates writing.