Use of “ist” or “sind” with “die Leute”

Question

In one of my German writing tests, I have the following sentence:

a) Die Umgebung ist sehr nett, jedoch ist die Leute ein bisschen unfreundlich.

This has been checked by my teacher and she says it is correct but it just sounds wrong. I would expect it to be

b) Die Umgebung ist sehr nett, jedoch sind die Leute ein bisschen unfreundlich.

since I believe Leute to be a plural. Although I am aware that German cannot always be translated into English, to me, this sentence would mean

The surroundings are very nice, however the people is a bit unfriendly.

However, there may be a simple German rule that I am not aware of. Who is correct?

Answer 1

Looking around I found this in http://german.about.com/library/weekly/aa021206a.htm

[Leute] is a common informal term for “people” in general. It is a word that only exists in the plural. (The singular of Leute is die/eine Person.)

Which seems to indicate that the correct form is

Die Leute sind

I have never seen die Leute ist.

Answer 2

I quote the vocabulary:

die Leute Pl., kein Sg.

die Leute, plural, no singular conjugation. So, I guess "die Leute ist" is wrong.