I honestly think YABU I'm afraid. There's a pandemic and people are dying in the tens of thousands, a plane crash full a day at least, day in, day out. The NHS is really struggling and there's reports of them running out of oxygen, really long waits for ambulances etc.
You ask where the spike was when they opened schools, see the graph attached. Secondary age children were the most infected group as of 18 Dec, closely followed by primary age kids. You can see how spread accelerated when schools re-opened and you can see the dip created by October half term.
If the government had opened schools more safely, we might not be in this position now, but we are where we are, there's a new variant, and it's spreading rapidly amongst children.
Where YANBU is to want support for vulnerable kids and working parents. This should be provided (I accept you're saying it wasn't in first lockdown) - write to your MP if you're not getting what you need, you should be, push the issue, get an advocate etc.
Parents and kids do need to be supported, but for the majority, right now, that shouldn't be through in person teaching. The more kids there are in school, the riskier it becomes. It's not fair to ask school staff to be putting themselves at this level of risk for kids that can safely stay at home. Besides which, the more kids that are in school, the more chance that there will be cases of covid and they will have to isolate at the drop of a hat, which gives no consistency for the kids, creates a nightmare for working parents due to the short notice, and is harder because you can't even take the kids out for a walk or to the park if they're isolating.
We shouldn't have all kids in school, with no distancing, no masks, and threats of fines to parents if they don't send them in the middle of a pandemic. Where this causes issues for families, we need to address those issues, not have a one size fits all approach. My child should not be forced into school because you feel that school is the best place for your child at the moment.
You also need to consider how you will cope if you get covid, and are poorly and needing to look after your kids in isolation, because that's also happening to people and is very difficult for them.
I think we need a short, strict lockdown including schools to get the levels right down, and give us chance to get vaccinations rolled out. NHS and care staff should be top priority, then school staff.
When the levels are lower, they need to look again at how to make schools safer - they're looking at testing in secondary schools now but I think the current plan to test close contacts instead of isolating them could actually make things worse, so it needs work. I'd like them to strongly encourage masks and look at a blended approach in secondary schools at least.
There's not really any easy answers because all of the possible situations are pretty crap really. But schools open, no ifs, no buts, isn't any good right now, it's not working and something has got to give I'm afraid.