The requirements of section 7 with respect to any elementary or secondary school or school system shall be deemed to be satisfied if such school or school system (a) is subject to a final order of a court of the United States for the desegregation of such school or school system, and provides an assurance that it will comply with such order, including any future modification of such order, or (b) submits a plan for the desegregation of such school or school system which the United States Commissioner of Education determines is adequate to accomplish the purpose of the Act and this regulation, and provides reasonable assurance that it will carry out such plans; in any case of continuing Federal financial assistance the responsible agency official may reserve the right to redetermine, after such period as may be specified by him, the adequacy of the plan to accomplish the purposes of the Act and this regulation. In any case to which a final order of a court of the United States for the desegregation of such school or school system is entered after submission of such a plan, such plan shall be revised to conform to such final order, including any future modification of such order.