This doesn't really feel (to me, anyway) likes it's a JFF question.
I sort of get the sense that if people here had said, 'yeah, i'd be so angry' that you might be inclined to admit to some anger here. Kind of like you are looking for others to put their stamp of approval on being angry with the school.
Sorry if this is not what you meant, but based on your recent posts, if I recall correctly, you've been angry about the parking lot and the principal as well as having some issues with a mom of an injured child being allowed to remain for so long in the classroom. So, when you ask how "we" would feel, it just feels to me that you're looking for justification. Saying in your SWH that you found it "a bit funny" that, too, sounds like you're hedging.
Mentioning your observation of incompetence in the office and adding that your friend is angry with the way the school handles things and asking whether you should feel differently--- all of these things tip the scale over to the impression that you do have some lingering anger and want to be supported in feeling this way. Again, sorry if you disagree, but those are your own words, and that's just where my thoughts went when I read this.
So, to answer your question: I would be grateful that they called me. I would assume that perhaps they didn't see the message and that is why they called the second time. I'd thank them and not give any more thought. If I had any concerns, I'd talk with staff, kindly, to ensure we are all on the same page. If I had any special instructions about giving my child medications in the future, I'd put it in writing and give it to the staff in the health office.