Why do kids have to take tests in school?

Children and adolescents take tests in school because it is a good way to measure their current knowledge.  These students study certain topics and testing is a way to measure how much knowledge is retained.  Tests are also ways to motivate students to try harder because tests are typically graded with a letter grade.  A is associated with a perfect score, F is considered failing, and a C is considered average.  These grades can act as motivators for students and create a friendly competition in schools and other  external study programs to see who can do the best.