(a) A special student-learner certificate shall be effective for a period not to exceed the length of one school year unless a longer period is found to be justified by extraordinary circumstances. These circumstances must be explained in detail at the time of application. While each such request will be considered on its own merit, it is anticipated that such authorizations would be limited to occupations requiring an extended period of specialized training;

(b) No certificate shall authorize employment training beyond the date of graduation.

(c) No special student-learner certificate may be issued retroactively.