I'l try to look at this from a purely practical view, imagining that I'm back in my maths clasroom again:
OK, so I'm about to teach a trigonometry lesson to a Year 10 class. In order to maintain 2 metres between the kids, I'll only have about of third of my normal class there. (i.e. 8 to 10 pupils, instead of 24 to 30). Since there aren't enough maths teachers to have three classes being taught simultaneously, where there used to be just one, that means re-timetabling so that I can see each third of the class at different times. That's not impossible but it can only work (unless we're given a lot of extra staff) if we've only got just one or two year groups allowed back into school. So we've already got most of the kids still not being able to come back to school anyway. However, let's move on . . .
I do my introductory stuff (akin to university lecturing, at the front of the class) and go through a few worked examples on the board. Then it's "Over to you, kids" time, as I ask my pupils to try working through a few questions for themselves. At this point it's ESSENTIAL that I can go around the class, looking over shoulders, to check that everyone has fully grasped what I've been talking about. (If I realise that LOTS of pupils are all making the SAME mistakes, I can simply return to the board and try to improve my explanations. However if it's just an INDIVIDUAL pupil who's going wrong, I need to LEAN OVER them to amend what's in their exercise book and explain things more clearly to them). So HOW, I ask, am I meant to accomplish all the 'monitoring' and 'correcting' while remaining 2 metres away from all of my pupils?
However I've managed it, let's assume that we've now come to the end of my trigonometry lesson and reached break time: HOW, I ask, am I meant to separate the groups of teenage girls, who're all huddling around their mobile phones to show off their favourite Youtube and TikTok videos to each other, while keeping both myself and them 2 metres apart? And just HOW am I meant to break up the fight, between the two teenage boys who're laying into each other, without getting in between them to push them apart?
Ok, break's over and, because someone has decided that we'll have Year 8 pupils in school as well, I've now got to teach a lesson on probability that requires my pupils to carry out experiments (of dice tossing, drawing counters out of a box, etc) while WORKING IN GROUPS.
Again, I ask, HOW am I meant to achieve that while keeping my pupils 2 metres apart and also keeping well away from them myself when I'm meant to be CHECKING that they're carrying out the experiments, and recording their data, correctly?
I've tried to ensure that what I've written above isn't pro-union, anti-union, pro-government, anti-government or anything else. I'm simply trying to explain why I'd need someone to give me a LOT of answers to my 'How?' questions above before I could effectively teach my subject specialism again.
Comments, anyone?