Should students who fail their classes be retained and have to repeat the grade

It is a matter to discuss later that whether the students who fail their classes be retained or have to repeat the grade.
First of all, it is necessary to investigate the cause factor of achieving low grades.Because there are many reasons behind achieving low grades in exams. If a student is High achiever in most subjects and having low grade in one or two of any subject; this means that subjects are not of his or her interest.In this case a student should be provided with a little relaxation.
On other hand if a student is achieving overall low grade; this indicates his/her lack of interest in study or careless behavior. In this case, a student should retain his/her classes or repeat the grade. As low grader not only harms himself but also the reputation of the institute as well.