Namechanged for this but was thinking recently about something that happened when I was a kid and it's only now I'm an adult with children of my own that it feels really weird, but not sure if times have changed since then (late 90s)
My Y6 teacher (female) lived fairly locally but In a different village. I happened to be friends with an older child who lived nearby which I mentioned in passing to my teacher who said something along the lines of 'oh you'll have to pop round one day'. Being that age I took her at face value and I somehow ended up with her address and we did indeed go round one day after school. I'm not really sure why. She gave us a drink and a snack, we chatted for a bit in her front room then left. I don't think we ever told our parents where we'd been, I expect they thought we were at the village park.
Absolutely nothing bad happened and I don't for a second think that she is unsafe in any way, but aibu to think on hindsight this was over familiar, inappropriate and probably broke all sorts of school safeguarding rules, or were things different back then?!
YANBU - That was weird and inappropriate even then
YABU - things were different then and she was doing no harm