No kids shouldn't be able to choose there own bedtime. They aren't responsible enough and will stay up too late. At school they won't be able to concentrate and will have a lot of trouble with tests and other important things. It will affect there health and if they wake up too late they will miss important meals and if they pack their lunch they may lose the essential time needed for packing their lunch, and as kids they need food to grow. Maybe some kids are responsible enough but the magority aren't. So kids shouldn't choose their own bedtime.
I think children should have a fixed bedtime, and have regular clock. As this, they can have spirit in the daytime.