Children should not be allowed to perform because it's exploitation. Often, parents try to live vicariously through their children and it causes a lot of problems for their children. The young should focus on their education and having fun as children. They should not be forced to have adult resonsibilities at such a young age.
Children should have the option to perform. Some children are natural performers and love the spotlight and opportunity. Noone should be forced or pushed to perform, but those who really love it and have the desire to do so, should be allowed to follow their dreams. Performing helps children gain confidence and other important life skills that would serve them in the future.