Section 11. The division of immigration and Americanization shall employ such methods, consistent with law, as in its judgment, will tend to bring into sympathetic and mutually helpful relations the commonwealth and its residents of foreign origin, protect immigrants from exploitation and abuse, stimulate their acquisition and mastery of English, develop their understanding of American government, institutions and ideals, and generally promote their assimilation and naturalization. For the above purposes, the division may co-operate with other officers and departments of the commonwealth and with all public agencies, federal, state or municipal. It may investigate the exploitation or abuse of immigrants and in making any investigation may require the attendance and testimony of witnesses and the production of books and documents relating to the matter under investigation. Subject to the approval of the department and of the commission on administration and finance, the division may make reasonable charges for any service rendered or material furnished by it.