A better mock can mean a worse GCSE

Every December, we give our students a piece of advice that sounds like the opposite of what a tutor should say. If you are going to make mistakes, we tell them, make them in the mock.

Why would anyone hope for mistakes? The answer is in the word itself. A mock is an imitation of the real exam, held months early so that nothing in it counts. A mistake in December costs a few marks on a practice paper and shows exactly what to fix. The same mistake in June goes on the certificate.

So a mock is a rehearsal, and a rehearsal is where things are meant to go wrong. The trouble starts when the results come home.

Two ways to misread a mock

If the grade is good, the whole house relaxes, and your child carries on exactly as before. If the grade is bad, the house can tip into something close to panic: a new tutor, a new timetable, a new method, and sometimes a parent who decides to teach the subject themselves for a few weeks.

In our experience, both reactions share one error. Each of them treats a practice paper as if it were the verdict.

A weak mock can have many causes. Perhaps a topic has not been taught yet. The paper may have been marked quickly, by a teacher with a hundred other scripts to get through, as we explain in Tuition Is Not School. Your child may have run out of time, slept badly, or met a question worded in a way they had never seen before.

Even with no change in what a student knows, a test score moves. A student who sat the same kind of test several times “will not get the same score each time”, as the assessment expert Dylan Wiliam puts it.^[1] Marking adds its own variation, most of all in English. In an Ofqual study of exam-board marking, the chance of receiving the exact “definitive” grade was 96% for one maths qualification and 52% for one English Language and Literature qualification. Nearly every grade was within one grade either way.^[2]

One December morning cannot tell you which of those causes it was, and a change made in a hurry can easily fix the wrong thing.

Feelings are not a plan

Why does a single grade push a family so hard in one direction? Part of the answer is that planning ahead is still a growing skill at sixteen. A study of 935 people aged 10 to 30 found that planning ahead “continues to develop into young adulthood.”^[3] In our experience, a teenager often decides what to do next by how they feel that week. A good mock feels like proof that everything is working, so nothing changes. A bad mock feels like proof that everything is wrong, so everything changes at once.

Adults are pulled the same way. In one study, university students expected their final-year thesis to take about 34 days. It took them about 56, and fewer than a third finished on time.^[4]

Parents feel the pull most after a bad result. Researchers who reviewed the evidence on homework found that parents “become more controlling when their children are having difficulty”. They describe a cycle in which this kind of help “undermines their motivation, engagement, and performance”.^[5] Help from home can raise results.^[6] The trouble starts when the help takes control.

The real priority is the summer exam. Because that exam is months away, it is easy to lose sight of. No certificate carries a mock grade. The grades that sixth forms and colleges check are the summer ones, and some universities still look at them two years later, as Manchester Says No and English Counts Too both show. Your child sits that exam once in the summer. English Language can be taken again in November, but by then your child will already have started at a college chosen on the summer grades.

So a mock is worth a great deal as a rehearsal and much less as a prediction. Even a teacher’s forecast is often a grade out. When teachers forecast their students’ GCSE grades in May, the forecast was exactly right 44% of the time, and most of the misses were too high.^[7] A mock shows where your child is strong and where they are weak, while there is still time to act. It cannot tell you the grade in August.

There is one case, though, where a good mock is genuinely bad news. It is the hardest case to spot, because everybody in the house is pleased. How could a higher score ever be worse than a lower one?

Doing well is different from learning

Is the difference between doing well and learning just a game with words? Decades of laboratory work say otherwise, and the finding has held up better than almost anything else in the study of learning.

Two researchers, Robert Bjork and Nicholas Soderstrom, reviewed the evidence and drew the distinction as sharply as it can be drawn. Performance is what you can do right now, while you are being taught or tested. Learning is what is still there weeks later, when you need it.

Their conclusion, in their own words, is that conditions during teaching “can have opposite effects on learning and performance.”^[8]

They chose the word opposite, which is much stronger than different. Some ways of working make a student look better now and leave them knowing less later.

The danger is that nobody can feel the difference while it is happening. The same review notes that people “mistakenly interpret their performance during acquisition as a reliable guide to long-term learning.”^[8] In other words, the feeling that revision is being remembered is no evidence that it will still be there later.

Two students, one mock

Consider two students preparing for a mock in three weeks, and ask yourself which of them you would rather your child be.

Student A spends the last four evenings on it, re-reading their notes again and again and memorising a set of quotations and an essay structure. The four evenings are intense but effective, and Student A walks into the mock with everything fresh and does well.

Student B has been working for months in shorter sessions, coming back to the same skills repeatedly with gaps in between, and has been corrected each time. In the week before the mock, Student B does not cram, and does a normal amount of work instead.

Student A may well score higher, because cramming genuinely works when the test is only days away.

The research on this is old and consistent. Studying everything in one block beats spreading it out when the test comes immediately afterwards, and loses to spreading it out when the test is delayed.^[9] Spacing practice out over time is one of the most reliably repeated findings in the whole field.^[10]

Now look at the calendar. The mock is three weeks away, but the real exam is six months away, so Student A has prepared for the wrong date.

Why the better mock can make things worse

The score itself does no harm, but what follows it can.

A good mock result tells a family that the current approach is working, so the approach carries on. Nobody goes looking for specific weaknesses, because the number said there were none.

Six months later the same student sits the real paper, without the fresh cram and on unseen material, and the result is a surprise to everybody.

The mock did not cause that result. It did, however, hide the problem, and it gave the student six months of confidence in a method that was never building anything that would last.

So a better mock can mean a worse GCSE. Doing well is never the problem in itself. The problem is that a score achieved by cramming is a measurement of the cram, not of the child.

So are mocks a waste of time?

Mocks are among the most useful things your child will do all year, for a reason the research makes very clear: sitting a test is itself one of the most effective ways to learn.

Roediger and Karpicke showed that “taking a memory test not only assesses what one knows, but also enhances later retention”, an effect so well established that it has its own name, the testing effect.^[11] Practice testing is consistently rated among the most effective study techniques available.^[12]

So the mock is valuable, and the real question is what it is valuable for.

A mock used as retrieval practice, where your child sits it, finds out what they could not do and then goes and fixes those things, makes a student better.

A mock used as a target to cram for, where the aim is to get the number up, feel reassured and move on, makes a student look better.

The exam is the same in both cases, but the outcomes are opposite, and the difference lies entirely in what happens in the fortnight either side of it.

Three questions to ask about a mock result

Whatever the number was, the useful questions are the same three.

1. What exactly went wrong? Ask about the specific things rather than the grade. Which question types lost the most marks? Was it running out of time, not knowing what the question was asking, or knowing it and not being able to write it clearly? A grade cannot tell you that, but a breakdown can.

2. What was revised in the week before? If the answer is “a lot”, treat the score as provisional, because it is measuring recent effort as much as lasting skill. Nobody has cheated; that is simply what a cram measures.

3. What has been fixed since? This is the question that matters most, yet it is the one almost never asked. A mock that finds four weaknesses and leads to four fixed weaknesses is worth more than a mock two grades higher that led to nothing.

Why the right way feels worse

Working in the way that actually builds skill, spaced out over time, coming back to things, being corrected and then doing it again, feels worse than cramming. It is meant to.

Researchers call these “desirable difficulties”: ways of working that slow you down and feel less productive, and that produce better long-term learning precisely because of the extra effort.^[13]

This is why a good programme can feel harder than a weekend of revision that felt great, because the weekend was aimed at how the work felt rather than at what it would leave behind.

We would rather your child’s confidence came from a skill that is genuinely there in June than from a number in December.

If you would like a proper breakdown of where your child actually stands — the specific skills, not just a grade — our free assessment takes five minutes.

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