My daughter was asked this during at least half of her interviews this year. She answered honestly and told them the other five schools. She was very intentional in her search, so the other schools should not be a surprise to the interviewer. They are all basically on the same level academically, offer a similar feel and experience, etc.
We didn’t even think to hide an answer or be vague - perhaps that will hurt her chances, but she was very open about her search.
One school did ask a follow up question during the parent interview and asked if she had a learning difference they should be aware of because she is applying to Proctor and they offer support services. We told them no, she does not receive support services in school and that she just liked the natural environment, kind community, and off campus programs offered there.