What is the ruling on requesting a retake of academic examinations to improve grades?

If retaking an exam does not entail a violation of school regulations or injustice to others, then there is no harm in it. Injustice would occur to other classes that were not given the opportunity to retake the exam, or to some students who achieved a satisfactory grade and would be burdened by retaking the exam, or whose grades might decrease as a result. So, if the exam can be retaken without injustice, there is no harm, and some systems allow retaking exams and recording the higher grade. However, if the school regulations prohibit retaking the exam, then permission from the administration is necessary.