EDIT: Why would you want to have children compete with each other on learning abilities? How does it help anyone? If a child is going to take a tad bit longer to understand than another child, I would rather the child take a bit longer to master than force the child to acquire the knowledge within a set duration. If they score 90% of the marks would you be happy that they scored 90% or unhappy that they could not master the remaining 10% and will never be given a second chance to do so? And what if your child crosses the passing marks of say 40%? Would you be happy that your child scraped through with passing marks or be unhappy that it never got that extra time to learn the remaining 60%? Not every child has the same grasping power. And by making learning a competition you are taking away the right to learn from a majority of these young children.
I would rather the child compete with others on what it has learnt on a practical basis rather than theoretical! Currently, scores only determine how much of the theory the child has been able to master. There is no process that examines how that theoretical knowledge has been used effectively throughout the lifespan of the learner which is actually more important.
Let them learn at the pace they are comfortable with. By making sure more children are properly educated we will, as a society, automatically reap the benefits of their future contributions. With competition, you are restricting the scope to the "gifted few" who will then have to bear the burden of the rest.