What is the ruling on a teacher giving private lessons to his students for a fee, knowing that he receives a salary for teaching them, and he differentiates between students in giving out questions, which negatively affects the performance of the rest of the students?

It is permissible for a teacher to tutor students outside of working hours, provided certain conditions are met: there is no favoritism towards the students, it does not lead to dereliction of his primary duties, and the educational institution does not prohibit it. However, singling out students for questions or other aspects of the teacher's primary work at school is not permissible and is considered cheating and a betrayal of trust. There is no sin upon him if what he specializes for the students of the courses is not among the matters imposed on him in his work.