because we could so easily vaccinate the most vulnerable first?
The most vulnerable in society have been
vaccinated... The delay with children was largely because the risk of the vaccine is comparable to the risk of Covid.
because we could so easily have masks in school (we have the masks)?
As we can see from Scotland, masks don't stop infections from growing. The best they do is temper they growth somewhat. So if the choice is 3 months to get population immunity in schools,
or 6 months for the same period end result but with masks, I'd go for the former.
because we don't actually want more illness in children and more children in hospital, even if we don't think they'll die?
With Delta, unless we are prepared to live in lockdown, or near lockdown, conditions forever, we won't be able to stop children from getting Covid. The only difference is timing. Restrictions just extend the inevitable...
because children have already suffered a lot this pandemic and it isn't fair to protect virtually all the adults and then infect almost all the children , deliberately, with a new disease, when we don't know it's long term side effects?
The only way to avoid children being exposed is for them to live a half-life of endless restrictions, with no end in sight for masks, and social activities heavily curtailed forever. You may think it's healthy for our children to live the rest of their childhoods in this very unnatural and heavily constrained way in the interests
of being certain there are no long term
implications (which by definition you can't be sure of for many,many years). I fundamentally disagree. Our children's lives are for living, not for hiding away scared of their own shadow as they forego anything resembling a normal childhood "just in case".