Is it permissible to help some students but not others in correcting exams, and is informing an official about this action considered fitnah?

The teacher must fulfill their trust and perform their duties to the fullest. As for assisting some students over others, the reasons for this are not clear. Is it due to their diligence and good behavior, or is it arbitrary? Is it authorized by the school administration or not? If the student's distinction in character or diligence is the reason for the assistance, then there is no objection to it. Schools often allocate grades for behavior and attendance; therefore, these grades should be given their due and not be added to exam grades. Accordingly, the legitimacy of the teacher's action is considered: if permissible, there is no harm, otherwise, it is not permissible for you to do so, and this should be clarified to the teacher so they stop it, and the school administration should be consulted for inquiry.