As a cadet ages, he automatically moves up the the next patrol. However, he will not receive the equivalent Shield until all relevant Junior Requirements or Senior AC’s (Accomplishment Courses) requirements have been met.
Link to the Officer’s Manual:
Pages 16 and 17 through 22: Requirements by Patrol for Junior Cadets, 1st to 5th grade.
Pages 16 and 22 through 104: Rankings and Requirements for Senior Cadets/Adults, 6th grade and up.