Should students be graded on effort or ability?

Students should be graded more on effort and not ability, because not everyone has an ability but everyone can try hard. Some people have an ability and put out no effort at all.

Still that being said there are somethings were ability is reward in spite of any grading system. For example a good painting by someone with an inborn ability will be more valuable than the painting created by someone who worked hard but had no ability.