In message , James
writes

At A level, marks are allocated for SPG (Spelling, Punctuation and
Grammar) in all papers involving prose answers, whatever the subject.
This has been the case for many years. I don't think the problem is lack
of incentive so much as lack of ability.

Yeah, about three marks.

Three marks per paper in each of 6 papers.

It can make a difference, but it probably won't.

On the contrary, with only 6 marks between grades in many subjects 3
marks are likely to make the difference of a grade for many candidates.

--
Paul Terry