I have not played organized basketball since I was in sixth grade and recently joined a church league. At our most recent practice one of my teammates said that on a free throw attempt a player cannot go into the lane until the ball hits the rim. It is my understanding that this rule only applies to the shooter and that everyone else can get into the lane once the ball has left the shooter's hand. Who is right?

Thanks in advance. And if this helps at all, we're playing PIAA rules.

This was a new rule at the high school level a few years ago to clean up action in the paint. Your teammates are correct, the lane is off limits to everyone until the ball hits something.
This is assuming that by PIAA you mean Pennsylvania High School, which would go by NFHS rules.