Why not watch on a computer / tv in the classroom?
Because any teacher will tell you that they spend that time monitoring behaviour and intervening as required. Not actually watching at all. Even more so if you have a set of very emotional children who have recently suffered bereavement or are just easily moved. One starts crying, they all join in. Noone sees anything and noone can be properly comforted.
This is an historical event. Those who want to watch it should be able to, and even those with no interest at all should be able to mark the event - if that's by ignoring it and taking a walk, fine. It's still there as a day to take in honour of the Queen and the magnitude of the event, no matter your opinions on the monarchy.
Stop being pissed off with schools and trying to shove it back on them when they have zero say. Be pissed off with the employers making you work it or use annual leave on it - it is at THEIR discretion, not schools! And some of you may still get that day at another point in time. Self employed people, I'm sorry but when you chose to go self employed one of the downsides was not being paid if ill, for bank holidays etc. It sucks but you did know that. People scrambling for childcare - I appreciate it's hard and short notice, but you have this same problem when your school shuts at 7:30am due to snow or boiler break down, just with less notice. You have to turn to plan b.
I will be watching at home with my primary aged children, glad that both they and I can watch properly, take note of the moment, discuss any questions and deal with any upset (and both were very upset at the announcement of her death, completely unexpectedly so.)
I say again: Be pissed off with the employers making you work it or use annual leave on it - it is at THEIR discretion.