I must be missing something. You went to the post office, with your son. You asked the agent to look up a zip code, and she directed you to the book that is provided in the lobby for just such a scenario. OK. This part is clear to me.

What is not clear is why the combined intellects of you and your son were not sufficient for you to open the book, find your state and city, and get the necessary information. You were *right there,* were you not? You are clearly literate, since you have written this letter, and while I'm no expert on children I think an eleven year old could reasonably be expected to use a reference book regardless of innocence.

I'm with Mr. Helpful on this one. You had a great opportunity to show your son how to use reference materials to find information, and to teach him about the zip code system, and you totally blew it.