25 U.S.C. § 66

The Commissioner of Indian Affairs, with the approval of the Secretary of the Interior, may devolve the duties of Indian agency or part thereof upon the superintendent of the Indian school located at such agency or part thereof whenever in his judgment such superintendent can properly perform the duties of such agency. The pay of any superintendent who performs agency duties in addition to those of his superintendency may be increased by the Commissioner of Indian Affairs, in his discretion, to an extent not exceeding $300 per annum.