[Excerpt] The fundamental cause of the low effort level of American students, parents, and voters in school elections is the absence of good signals of effort and accomplishment and the consequent lack of rewards for learning. In most other advanced countries mastery of the curriculum is assessed by examinations that are set and graded at the national or regional level. Grades on these exams signal the student's achievement to employers and colleges and influence the jobs that graduates get and the universities and programs to which they are admitted. Exam results also influence school reputations and in some countries the number of students applying for admission to the school. In the United States, by contrast, students take aptitude tests that are not intended to assess the learning that has occurred in most of the classes taken in high school. The primary signals of academic achievement are diplomas awarded for time spent in school and grades and rank in class—criteria that assess achievement relative to other students in the school or classroom, not relative to an external standard.