I have one question to all the people complaining they 'don't want to' because they 'feel hot', 'panicky', 'faint' or get 'air thirst'.
How do you feel about Anti-Vaxxers?
I'll put money that a large percentage of those currently snowflaking around about 'not wanting' to wear masks (NOT those who really, genuinely can't) would also agree that parents who choose not to vaccinate their completely healthy kids are outrageous and should be prevented from sending kids to state schools etc or anywhere they mix with your kids.
Take a look at yourselves if you are - because this is the same thing. The general population is being asked to take a tiny bit of risk and a bit of discomfort to enable herd-level protection for those in society who genuinely can't.
A lot of those people, including a lot of children, will be those who have been shielding. We're out and about more, we're mixing, we're relaxing restrictions and this group is moving towards being able to come outdoors and back into society. If this step will make it safer for those individuals (and it will), then I see it as the decent thing for others to do.
I would support an official exemption card - not because people should have to explain their medical issues to others, but because it would stop them having to do just that. It would also deter a percentage of chancers from piss-taking if they thought they could be asked to produce it and prosecuted if they couldn't.
And, fwiw, I actually would support school children wearing masks when they return in September, probably from KS2 onwards. My 10 year old got used to hers when out and about very quickly, and it would be an extra layer of protection for them, for school staff and for the children in their classrooms who are more vulnerable. I strongly think it would hugely cut down on transmission of other winter bugs as well.