In reply to "Do they have...", which is correct — "yes, they do" or "yes, they have"?

My daughter is in an 5th grade English class in Germany with a teacher who teaches British English.

The teacher asked what is the correct response to

Do they have some?

My daughter, who has learned mostly from hearing American English spoken, responded:

Yes, they do.

The teacher said that she should instead say:

Yes, they have.

What is going on here? Is this a difference between American/British English or is one of these more correct than the other?

Solution 1:

Your daughter is correct: in standard British (or US) English, it should be “Yes, they do.”

The key here is that do, not have, is the auxiliary verb. Have can sometimes be an auxiliary, but in this sentence it’s the main verb. So:

“Do they like pizza?” “Yes, they do.”

“Have they had lunch yet?” “Yes, they have.”

“Do they have some?” “Yes, they do.”

(In some dialects, your teacher’s form would be fine; also, it was quite standard historically. But I think (though I’m not sure) that most speakers who’d use that form would also pose the question differently, inverting the main verb without using an auxiliary do, and would still match the verb of the answer to the initial verb of the question: “Have they any?” “Yes, they have.” parallel to “Heard ye the tidings?” “Yes, I heard.”)

Solution 2:

Correct answers would be either "Yes, they do." or "Yes, they have some.". "Yes, they have" would be an appropriate answer to, say, "Have the done that yet?".