For anyone else with this problem:
I had the “&” symbol in the title of some of posts, and as a result, it added those posts to get_posts even if the category didn’t match. Strange!
I tried disabling EventCalendar3, and now my Search works just fine. Does anyone know of any incompatibilities with EventCalendar3 and WordPress Search?
Yes, that’s the way it’s supposed to work.
However, posts such as “Uniforms & Spirit Items” belong only in ADMISSIONS and not in ABOUT. I don’t understand why it would show up in both categories! Thanks for your help!