That might not be a bad idea. But it still doesn't solve the problem of some people learning/advancing quicker than others.

Why is that inherently a problem? Some people will always learn/advance quicker than others in just about any are of life for a variety of reasons. The only way to "solve" that problem generally would be some very dystopian form of social control.

I fully support kids being able to advance as quickly as they can or want to. The current system does not support that.

In many ways we're already at an always pass system.