Written by a practising AQA examiner and Senior Curriculum Manager for English
Ask a student what “sentence demarcation” means and most will guess it is a grammar term they were never taught. It isn’t. It is the mark scheme’s word for something much simpler: does the student know where a sentence starts and where it ends, and can they show it every single time, not just when the sentence is short and easy.
It sits inside AO6 — worth 16 marks on each of the two writing questions, 32 marks across the whole GCSE, a full fifth of the qualification — alongside range of vocabulary, range of punctuation and range of sentence forms. Of everything in AO6, demarcation is the most fixable. It isn’t really a writing-ability skill. It’s a habit, and habits respond to drilling faster than anything else on the specification.
What examiners are actually looking at
Examiners are not counting full stops. They are watching whether a student’s control of sentence boundaries holds up as the writing gets more ambitious. Almost every student can demarcate a short, simple sentence correctly. What separates the four levels is what happens when the sentence gets longer, when it carries a subordinate clause, or when the student is writing quickly under time pressure and stops thinking about it.
The four levels, in plain English
| Level | What’s actually happening | What it looks like on the page |
|---|---|---|
| 4 | Boundaries are controlled and accurate throughout, including inside long or complex sentences | A 30-word sentence with two subordinate clauses still ends exactly where it should, followed by a capital letter starting the next one |
| 3 | Accurate for most of the response, with the odd slip | One or two run-on sentences appear, usually in the excitement of a strong paragraph, but the rest of the piece is controlled |
| 2 | Inconsistent — secure in short sentences, breaks down in longer ones | Simple sentences are punctuated correctly; anything more ambitious drifts into a comma splice or a run-on |
| 1 | Demarcation shows up only occasionally | Full stops and capitals appear sometimes, more by chance than by control; long unpunctuated strings of clauses are common |
The gap between level 2 and level 3 is almost always the same fault, appearing again and again across scripts: the comma splice.
The one mistake that costs the most marks
Phones cause more disruption than they solve, teachers spend half the lesson managing them.
That sentence reads perfectly naturally, which is exactly why students don’t spot it. Two complete ideas have been joined with a comma, when a comma isn’t strong enough to do that job. It needs a full stop, a semicolon, or a conjunction:
Phones cause more disruption than they solve. Teachers spend half the lesson managing them.
Phones cause more disruption than they solve, so teachers spend half the lesson managing them.
This single error, repeated three or four times across a response, is usually the reason a student who is clearly capable of level 3 or 4 writing gets capped at level 2 for technical accuracy. It costs more marks than almost any other single fault in AO6, because it isn’t marked as one mistake — it’s read as evidence that sentence boundaries aren’t under control.
This is exactly what our Sentence accuracy and punctuation workbook drills — comma splices, run-ons and boundary control, worked through error by error, with the examiner reasoning for why each one loses marks.
What to practise this week
Take a piece of writing the student has already produced. Don’t correct it for them — hand it back with every full stop and comma highlighted, and ask them to explain out loud why each one is there. If they can’t explain a comma, it’s usually doing the job of a full stop and shouldn’t be there. This single exercise, repeated on three or four pieces, does more for demarcation than any worksheet, because it forces the decision to become conscious rather than instinctive.
Demarcation is also the one part of AO6 that survives time pressure the worst. It is worth practising the last two sentences of a piece under a countdown, since that is where control most often slips in the exam itself.
The next post in this series looks at the other half of AO6 that examiners weigh separately: what a “wide range of punctuation” actually means, and why range and accuracy are judged as two different things.