> teachers in those schools, regardless of their ability, have to respond to parents immediately.

Or else what? Their union will hold them to account? Their colleagues? Their administration?

I have two kids in such public schools and I can’t think of anything I’d ask of a teacher that would require a same-day response let alone an immediate one.

If I need an immediate response, it’s not likely a topic I should be taking to a teacher in the first place. Their job is to teach, not to monitor for inbound comms from parents.

By 'immediate', I meant same day. But you sound like a reasonable parent; you're writing in the hypothetical. It's the small minority of parents who are constantly in contact with teachers (because most legitimate concerns should be triaged by the school receptionist) and consequently cause the problems - it's no different to any other customer-facing role.