All expenditure of money herein or after April 30, 1908, appropriated for school purposes among the Indians, shall be at all times under the supervision and direction of the Commissioner of Indian Affairs, and in all respects in conformity with such conditions, rules, and regulations as to the conduct and methods of instruction and expenditure of money as may be from time to time prescribed by him, subject to the supervision of the Secretary of the Interior.
[Apr. 30, 1908, ch. 153], [35 Stat. 72].)