Question for British list members/PS for Goddlefrood

[Carol]

Carol earlier:

> > Carol, noting that in the U.S., fifth grade (which I assume
corresponds with Year 5) is comprised mostly of ten- and
eleven-year-olds (they'd be ten at the beginning of the year but most
will have turned eleven by this point in the school year)
>  
> Geoff:
> Year 7 corresponds to the old First Year which is for children who
reached 11 in the currency of the previous school year.
>
<snip>> 
> For cross-reference, the UK exam year when pupils take GCSE exams
and reach the age of 16 in that year is Year 11 (the old Fifth Year).
> 
> The all-through class numbering system became generally used in the
UK round about 1989/90.
>
Carol responds:
So children enter what we would call first grade and you call Year One
at age five rather than age six?

In the U.S., they enter kindergarten (half-days of school) at age five
and first grade at age six. Most students are eighteen when they
graduate from high school, though about one fourth (those with summer
birthdays) are still seventeen.

I'm not sure what GCSE exams are. Our high school students take SATs
(Scholastic Aptitude Tests) or in some cases, ACTs (I've forgotten
what it stands for--academic something-or-other tests, probably) in
senior year, that is, twelfth grade.

Do British schools have a Year Twelve, or do students finish school
and start university (or get a job) at seventeen (sixteen for those
born in summer) rather than eighteen (seventeen for the summer-borns)
as in the U.S.?

Carol, wondering, if that's the case, why England doesn't just follow
the WW's example and have kids come of age at seventeen :-)