
Sounds like the grammar was correct without editing is to are, however, it does come out sounding unusual. I would have gone with "Gerty Hawk Chocolates has arrived!"....or would it be "have" lol. English language is so willy nilly at times, it must be tough to learn as a second language with all these odd rules.
Let me explain why
something was wrong with the construction. It's subject/verb agreement that we're talking about, so first we have to determine the subject of the sentence. Here's the sentence as Scott originally gave it to us: "Gertude [sic] Hawk Chocolates is Here!"
The first question is, is the subject "Gertrude Hawk Chocolates" or just "Chocolates"? We might be able to use capitalization as a hint (i.e., the capitilization of "Chocolates" might mean that it's part of the company name), but because the word "Here" is also capitalized, that idea is out the window.
Nonetheless, let's assume that the subject is 'Gertrude Hawks Chocolates." If that's the case, "is" would be correct. The problem is that
if the sentence is correct as cast, we should be able to assume either that the company itself is present, or that a representative of the company is present. Remember--we're saying that the subject of the sentence, with which the verb must agree, is the company name, and not its products or catalogs. If neither of those things are true, then the sentence is grammatically correct, but
factually incorrect.
Because we now know that (A) the company itself wasn't present; (B) a company representative wasn't present (or at least wasn't being referred to) and (C) the chocolates weren't present either, the subject of the sentence is wrong. The meaning someone intended to convey is that
catalogs were present. In other words, the person who made the sign didn't provide the necessary information. It doesn't matter that everyone knew what was meant; we're talking about the rules of grammar here, and in some contexts this might be pedantic overkill, but I think that signs hung in schools should be grammatically--and factually--correct.
So the person who corrected the sign made the wrong correction. The sign should have been changed to read "Gertrude Hawks Chocolates
catalogs are here!" The questions of (A) what's actually present and (B) subject/verb agreement are thus eliminated.