No provision of any applicable program shall be construed to authorize any department, agency, officer, or employee of the United States to exercise any direction, supervision, or control over the curriculum, program of instruction, administration, or personnel of any educational institution, school, or school system, or over the selection of library resources, textbooks, or other printed or published instructional materials by any educational institution or school system, or to require the assignment or transportation of students or teachers in order to overcome racial imbalance.