HR calling me on my day off

You have nailed the issue for the OP - she doesn’t want to talk about it in her day off as it is her free time: HR were wrong to contact her, out of the blue about this.

OP - talk to your union and bring representation with you going forward to any meeting, you know for off the record note taking..

Ok so by the sounds of it, this could well be your HT initiating this and I too, would be suspicious. I would definitely seek advice from your union and you are within your rights to bring a union representative with you to any meetings that HR is present at, you are also allowed to delay the meetings until a union rep is available, in my experience it’s within a week or so so not unreasonable. I’d try and keep communication over email so there is a paper trail, take photos too. I once had an a really unpleasant email from my HT magically deleted.
I hope you get to focus on your health.

Op

you are seriously overreacting here

its not that deep

Not the end of the world if they did. I'd have a chance of hearing them, for a start.

My last Occy Health appointment was after I finished work and my Access to Work contact is all done outside school hours.

I couldn't get worked up about it they are trying to support you not asking you to work so what would be the difference if they called then or your lunch hour.
Personally I'd rather discuss private matters from the comfort of my home rather than a staff room of classroom anyone could walk into or overhear.

Would you have complained if they had called when you were on a lunch break, or a free period or asked you to come in before school or after school?

I think you would.

I think your reaction is disproportionate and you’re taking the worst possible read for everything. That’s certainly not surprising if you’re dealing with PMDD.

They called once during their normal working hours and left a voicemail, assuming you’d listen to it before choosing when to call back at a time that also worked for you. If you had picked up initially they likely would have started with “is this a good time to talk or…” but when you called back they likely (and reasonably) assumed that was your indication you were ready to talk then. It’s not their fault you didn’t listen to the voicemail, though I understand why you didn’t.

I’m always one to remind employees that HR works their employer, so being aware of what you say to them is important. But calling to make sure you were ok with the any arrangements in place and not in need of additional support is very normal and something HR should do, so the assumption that the motives were nefarious is not reasonable. You’re running with the worst possible interpretations of all of this.

OP I work in a school and can confirm that is quite unusual to have unsolicited chats with HR. You are probably right to be on your guard. However I would just make a note of what was said. I would also ask your line manager about the reason for the call. In future ask them to email you during work hours to agree a time that works fir a telephone conversation.

Kindly OP, if you're not able to react proportionately to a VM and admit you're "not well", then perhaps there are some performance concerns?

I don’t think it’s unusual for a line manager to ask for HR support if they feel unsure about how to offer effective support.

If you had picked up, HR might well have opened with “is now a good time or would you prefer to speak in school?”

As you called back after they left a voicemail, it’s not unreasonable that they thought you had listened to it and were OK to talk to them, so they launched into their conversation

This is totally on you. You could have checked your VM and not returned the call.

If HR want her to have time to speak freely then it is their job to facilitate this within her working hours, ie they should arrange cover for a lesson that she is scheduled to teach on a day she is in work, not on her day off when she is not being paid.

I cannot believe how ridiculous some people being here.

Yes they definitely shouldn’t have interrupted your day off they should have sent you an email to tell you exactly what they wanted and asked to arrange a time within your working hours or if that’s really impossible asked you when you would be happy to speak. It’s probably just that they thought oh this is
a good time for me to call and not even considering you but understandable it makes you feel nervous about what’s going on.

Surely your day off is the one day you are likely to have tome to speak freely. It is not ideal, and presumably the voicemail requests a call back at your convenience.

If you are not full time it is reasonable for HR to check your non-working days. I am not surprised to read of your suspicions.

Would you be happy for HR to phone you on a Sunday afternoon when you are more likely to be free? As this similar to what you are suggesting?

Don’t call back random numbers if you don’t want to speak to them!

HR can't win.

Other scenarios where they would be accused of nefarious behaviour could be 'I disclosed the need for accommodations and HR never reached out to me to discuss', or 'HR called me on a day I was teaching class, how could they expect me to be available?'

They called your personal number when you were most likely to be free and more able to ensure you had privacy to take the call.

I don't want to have conversations in the day where anybody could walk in, Year 9 could overhear or I've got a data drop deadline.