The basic ruling is that it is permissible to
receive a fee for teaching the Qur'an. This is because of the generality of the Hadith of the Prophet (peace be upon him):
The most lawful thing for which you receive payment is (teaching) the Book of Allah.
Al-Bukhari in his Sahih)Accordingly, it is permissible for you to accept the money that is given to you by the guardians of the children as a sort of a gift for teaching and helping the children memorize the Qur'an. Doing so will not deprive you of the abundant and great reward of Allah for your efforts, so long as you have a faithful intention to act sincerely for the Sake of Allah (Exalted be He) and are keen to inculcate into children virtuous manners.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.