M1, A1, B1: what the letters in a mark scheme actually mean

Every teacher tells you to check your work against the mark scheme. Almost nobody teaches you to read one, which is a strange gap, because a mark scheme is not written in English. It is written in a compressed notation designed for examiners who already know the code.

Once you can read it, two things change. You stop arguing with yourself about whether your answer “counts”, and you start seeing that the marks were laid out in a specific order that your working either matched or did not.

Here is the code.

The three letters that do most of the work

Nearly every mark on a maths or science paper is one of these.

M is a method mark. It is awarded for doing the right thing, whether or not it produces the right number. If the scheme says M1 for correct substitution into the quadratic formula, then substituting correctly earns that mark even if you then make an arithmetic error and end up with the wrong roots.

A is an accuracy mark. It is awarded for the correct value, and it is almost always dependent on the method mark before it. You cannot earn A1 for a right answer that arrived by a method the scheme does not recognise, and you generally cannot earn it at all if the M1 was not earned.

B is a standalone mark. It is independent, awarded for a correct statement or value on its own, with no method required. Naming a piece of apparatus, stating a unit, writing down a value read off a graph. B marks are the cheapest marks on the paper and the ones most often left blank.

Some schemes add a fourth, and the letter varies by board and by subject, so check yours:

A mark for communication or reasoning. On a “show that” question or a proof, part of the credit is for the argument being stated and followed through rather than for the numbers. Where a scheme awards this it will say so explicitly in the notes column.

Why this matters more than anything else you know about mark schemes

Read this line from a typical scheme for a question worth 4 marks:

M1 for a complete method to find the surface area A1 for 158 (or 157.9 to 158.0) M1 for dividing by 45 A1 cao for 3.5

Four marks, four separate decisions, made independently. A student who sets the problem up correctly, makes a slip in the arithmetic, and finishes with the wrong number earns two of those four marks. A student who writes the correct final answer with no working at all may earn fewer, because the M marks have nothing to attach to.

That is the single most useful fact about exam marking, and most students go into the exam not knowing it. The scheme is not looking at your answer. It is looking for a list of things, in order, and ticking off the ones it can find.

The small print that decides your marks

These abbreviations appear constantly and each of them changes what you have to write.

• ft, or “follow through”. If you got an earlier part wrong and then used your wrong value correctly in this part, you still get the credit. This is why you should never abandon a question just because part (a) went badly. Part (b) is often marked ft.
• cao, “correct answer only”. The opposite. Only the exact stated answer scores. No follow through, no near misses. When you see cao you are being told that precision matters here and rounding early will cost you.
• oe, “or equivalent”. Any mathematically equivalent form is accepted. 1/4 and 0.25 and 25% are the same mark.
• ORA, “or reverse argument”. Common in science. If the scheme says “the rate increases because particles collide more frequently”, then saying it decreases because they collide less frequently is the same mark, provided you are answering the direction the question asked about.
• dep, “dependent”. This mark cannot be awarded unless the one it depends on was. It is usually written M1dep or A1dep.
• isw, “ignore subsequent working”. You reached the right answer, then kept going and made it worse. The examiner takes the right answer and ignores the mess after it. Useful to know, and not something to rely on.
• Words in brackets are optional. “(the) rate of reaction increases” means you do not need the word “the”. Words separated by a slash are alternatives: any one of them scores.

The mark scheme is not the answer sheet

This is the mistake that makes self checking useless.

A mark scheme is a list of creditable points, not a model answer. It is frequently shorter, uglier and less complete than a good response would be. It says things like “any two from” followed by six bullets. It says “accept any valid alternative”. It contains a right hand column of examiner notes that is often where the real information is.

So when you check your work and your answer does not look like the scheme, you are asking the wrong question. The question is not “does my answer match this?” It is “can an examiner find each of these points somewhere in what I wrote?”

Those are very different tests, and the second one is the one being applied to your paper.

How to actually use one

Try this on the next past paper you mark yourself.

1. Mark the question before you read the scheme. Write down what you think you deserve and why. Then open the scheme. The gap between your two judgements is the thing you are actually learning.
2. Award the marks one at a time, in the scheme’s order. Do not decide “that is roughly a 3”. Go line by line: M1, can I find it? A1, can I find it? This is what an examiner does and it produces a completely different result from a general impression.
3. For every mark you did not award yourself, write one word for why. Not there. Not clear. Wrong. Those single words, collected across a paper, are your revision list.
4. Look specifically for M marks you nearly had. A method you performed but never wrote down is the most recoverable mark in the whole exam, and the only fix required is a habit.

The honest problem with doing this alone

The method mark is where self-marking breaks down. You look at your half-finished working, you look at the scheme, and you genuinely cannot say whether what you wrote is the method the M1 describes or something that merely resembles it.

That is not a willpower problem and being stricter with yourself does not fix it. It is worth understanding properly, because it is the reason a self-marked score runs quietly generous: marking your own work is harder than it looks.

What it does not do is make self-marking pointless. It makes the codes above worth learning properly, because the better you read the scheme, the smaller that gap gets.

If you are teaching this

Ten minutes and one question is enough. The class marks it blind, then the scheme goes on the board line by line. When a wrong answer turns out to be worth three marks of four, the point lands harder than a term of being told to show your working.

Marky’s feedback explains each question against the scheme, naming the marks it uses where it can, so a student sees what was awarded, what was refused, and why. See how that looks.