(a) Except for active participatory courses in physical education, visual arts, or performing arts, if a community college district offers credit courses for variable units on an open-entry/ open-exit basis pursuant to section 58164, the district policies and procedures on course repetition adopted pursuant to section 55040 shall provide that a student may enroll in the course as many times as necessary to complete one time the entire curriculum of the course as described in the course outline of record. District policy may not permit students to enroll more than one time in an active participatory course in physical education, visual arts, or performing arts pursuant to this section. District policy may not permit the student to repeat any portion of the curriculum for the course, unless:

(b) When course repetition of a portion of a course is permitted under the circumstances described in subdivision (a), the district policy may allow the previous grade and credit to be disregarded in computing the student's GPA.