Is it permissible for a female Quran memorization teacher who does not receive a salary to accept a gift (gold or otherwise) from her students at the end of the academic year, knowing that refusing it might dishearten them?

If the student will be leaving the school, then there is no harm in the gift. However, if the teacher-student relationship will continue, it is feared that the gift may cause the teacher to show favoritism towards the student and not be just among the students.