so … a …
There is another rather formal structure with so + adjective + a/an + noun (see 14).
I had never before met so gentle a person. (= … such a gentle person.)
This is from Michael Swan's "Practical English Usage".
I wonder whether we can write it for plural noun.
For example.
1."They are so beautiful a teacher''.
2."They are so much beautiful teachers"
3."She is so much a beautiful teacher."
Best Answer
You have probably realised by now that English is not consistent, full of little rules that are often poorly articulated - with a lot of exceptions, words or phrases that don't behave like others, not to mention all the confusion of there being words that can be proper verbs or auxiliary verbs. So it shouldn't come entirely as a surprise that this is a phrase that doesn't work with all verbs.
"So X a Y", with X an adjective and Y a noun - generally a common noun, a noun that refers to a type of thing in general (like dog, map, diploma, idea etc.). It forms a noun phrase referring to some specific instance and means that, of the category Y, the specific instance being referred to is unusually Y.
The song that she sang was unusually sweet.
The horse that he rode was unusually fast.
Actually, most of the times I've seen it used, it's code an extra bit after the help you understand just how X that particular Y is/was:
It can also be used to indicate degree relatively:
However, it seems to be increasingly used without that that-clause, or any other sort of comparison or degree indicator, simply to mean that the Y in question was very X. Which is a shame, to my mind, because the full thing is much more poetic, but c'est la vie, language changes, and it was ever thus.
Now, it doesn't work with plurals. I know people have mentioned "I had never met so gentle a people", but look at the indefinite article - people here is singular, not plural. It's a bit of a quirk for that word - people can be the plural of person, or it can be a singular noun referring to a large, at least vaguely defined group of people, typically connected by some sort of kinship, such as an ethnic group or a nation, or sometimes the members of a particular religious group (possibly thanks to the quotation "a peculiar people"). The potential confusion is such that in some dialects, persons is increasingly used when you want to be clear that you are referring to several people as a collection of individuals, rather than a singular mass of people who are connected in some way.
You can't use it with plurals; there is no alternative to the a/an that is part of the formula. So you can't do it for several teachers.
You also don't generally use it with is, or possibly (I'm not 100% on this) any form of to be. There may be other verbs you can't use it with, but I can't think of any right now. However, negating the verb usually makes it okay, as one of the commenters explained.
The alternative that doesn't suffer from these limitations is such.
Your option 3 just makes no sense. Sorry.
You can even use such in the degree-indicating or comparison cases:
However, there is a certain undeniable poetry to "so X a Y".