Q. I am an elementary school teacher and am confronted with an abbreviation debate. How should the abbreviation of United States of America be taught? I am finding that it is acceptable in several forms, but I would like to be as accurate as possible.

A. I appreciate the difficulty of a teacher who wants to present children with what’s “correct,” but I’m afraid there is no single right answer to your question. Chicago style is USA (without periods), but we also accept both US and U.S. Other authoritative style manuals and dictionaries vary in their recommendations. Please see CMOS 10.4 and 10.33 for guidelines and discussion. Maybe you could show your class the choices and vote on your own house style.