> "Their annual health assessments". Is that something everyone, or maybe every student, in the UK has?

No. It's badly phrased in the article but the annual health assessment is something being done as part of this research, nothing bigger

In Germany there are a few key milestone years that are heavily documented (forget which years) and every kid has to do that with their pediatrician. In the US it's typical to have an annual exam with their pediatrician - this is free and standard for everybody with health insurance (which includes medicaid and state programs). Unlike Germany though I think a parent could be disengaged and that would mean multiple years without a checkup. In Germany I think they'd know and check in on the family if those milestone checkups weren't done.

Not really.Maybe if you are over certian age, but you can barely get a GP appointment when you need it.