I truly think that it depends on the child and the group of kids. I have a 13yr old son, and I would definitely let him go to the movies with a group of boys- just the movies though- no roaming the mall or anything. I also have a 10yr old daughter and an 8yr old son, and unless they had an adult with them, they would not be allowed to go. I think that they would do just fine if everything went as planned, but if something out of the ordinary were to happen, I can't be sure of how they might react. I think they still need guidance especially if something out of the ordinary did occur.
Thankfully, this has not been an issue in our home. They have ever asked to go to the movies with just a group of friends....