Is attending mixed classes considered sinful, even with one's disapproval and rejection of it? And should a competent teacher be abandoned due to their involvement in mixed-gender settings?

It is permissible to enroll in mixed-gender educational centers out of necessity and if a non-mixed alternative is unavailable, provided that one lowers their gaze, guards their tongue, and avoids causes of temptation. A Muslim must enroll in non-mixed centers if they exist. If a man is more capable or efficient in a specific field, it is permissible for a woman to go to him, even if there is a woman in the same specialization. However, if a Muslim fears temptation and falling into sin, they must leave mixed-gender centers, even if they are scientifically superior, because safeguarding one's religion takes precedence over other interests.