; and (B) may include a program of education at an institution of higher learning if the Secretary determines that the program of education is predominantly vocational in content. (2) Exclusions A vocational training program under this section may not include the provision of any loan or subsistence allowance or any automobile adaptive equipment. (d) Program duration (1) In general Except as provided in paragraph (2) and subject to subsection (e)(2), a vocational training program under this section may not exceed 24 months. (2) Extensions The Secretary may grant an extension of a vocational training program for an eligible descendant under this section for up to 24 additional months if the Secretary determines that the extension is necessary in order for the descendant to achieve a vocational goal identified (before the end of the first 24 months of such program) in the written plan of vocational rehabilitation formulated for the descendant pursuant to subsection (b). (3) Commencement A vocational training program under this section may begin on the eligible descendant's 18th birthday, or on the successful completion of the descendant's secondary schooling, whichever first occurs, except that, if the descendant is above the age of compulsory school attendance under applicable State law and the Secretary determines that the descendant's best interests will be served thereby, the vocational training program may begin before the descendant's 18th birthday. (e) Relationship to other programs (1) In general An eligible descendant who is pursuing a program of vocational training under this section and is also eligible for assistance under a program under chapter 35 of this title may not receive assistance under both such programs concurrently. The descendant shall elect (in such form and manner as the Secretary may prescribe) the program under which the descendant is to receive assistance. (2) Aggregate period The aggregate period for which an eligible descendant may receive assistance under this section and chapter 35