The Teachers Toolbox – Resources

Professor John Hattie’s Table of Effect Sizes

Hattie says ‘effect sizes’ are the best way of answering the question ‘what has the greatest influence on student learning?’. An effect-size of 1.0 is typically associated with:

•  advancing learners’ achievement by one year, or improving the rate of learning by 50%

•  a correlation between some variable (e.g., amount of homework) and achievement of approximately .50

•  A two grade leap in GCSE, e.g. from a 4 grade to a 6 grade

An effect size of 1.0 is clearly enormous! (It is defined as an increase of one standard deviation)

Below is a small selection of Hattie’s table of effect sizes. (Source: The Research of John Hattie where you can access the full list)

Influence Effect Size Source of Influence
Self-reported grades 1.33 Student
Teacher estimates of achievement 1.29 Teacher
Cognitive task analysis 1.29 Teacher
Piagetian programs 1.28 Teacher
Student’s prior cognitive ability .98 Student
Direct instruction .82 Teacher
Feedback .74 Teacher
Acceleration .72 Student
Behavioural intervention programs .62 Teacher
Mastery learning .61 Teacher
Challenge of Goals .59 Teacher
Working memory strength .57 Student
Class management .56 Teacher
Student’s concentration/persistence/engagement .54 Student
Positive peer influences .53 Peers
Postive family / home dynamics .52 Parents
Teacher – student relationship .52 Teacher
Peer tutoring .51 Teacher
Questioning .48 Teacher
Practice testing .46 Teacher
Perceived task value .46 Teacher
Simulation & games .34 Teacher
Homework .29 Teacher
Individualisation .23 Teacher
Audio-visual methods .22 Teacher
School finances/money
Co or team teaching .19 Teacher
Programmed instruction .18 Teacher
Reducing class size .16 School
Student control over learning .02 Teacher
Student feeling disliked -.19 Teacher/Peers


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Terms used in the table (Interpreted by Geoff Petty)

•  An effect size of 0.5 is equivalent to a one grade leap at GCSE

•  An effect size of 1.0 is equivalent to a two grade leap at GCSE

•  ‘Number of effects is the number of effect sizes from well designed studies that have been averaged to produce the average effect size.

•  An effect size above 0.4 is above average for educational research

The effect sizes are averaged, and are a synthesis of research studies thought to be well designed and implemented by research reviewers. Hence they are the best guess we have about what has the greatest effect on student achievement.

Some effect sizes are ‘Russian Dolls’ containing more than one strategy e.g. ‘Direct instruction’ is a strategy that includes active learning, structured reviews after one hour, five hours and 20 hours study. There is also immediate feedback for the learners, and some corrective work if this is necessary.

Hattie does not define most of the terms in his table. My understanding of them is:

Feedback Hattie has made clear that ‘feedback’ includes telling students what they have done well (positive reinforcement), and what they need to do to improve (corrective work, targets etc), but it also includes clarifying goals. This means that giving students assessment criteria for example would be included in ‘feedback’. This may seem odd, but high quality feedback is always given against explicit criteria, and so these would be included in ‘feedback’ experiments.

As well as feedback on the task Hattie believes that students can get feedback on the processes they have used to complete the task, and on their ability to self-regulate their own learning. All these have the capacity to increase achievement. Feedback on the ‘self’ such as ‘well done you are good at this’ is not helpful. The feedback must be informative rather than evaluative.


Students prior cognitive ability: This is IQ and similar measures


Acceleration I think this is very bright students being put forward a year in schools


Mastery learning A system of tests and retests of easy material with a high pass mark, if a student does not pass they must do extra work and then take a retest on the material they were weak at. See Teaching Today by Geoffrey Petty.


Questioning Students being questioned. The most effective questions are high order ‘why?’ ‘how?” and ‘which is best?’ questions that really make students think . They need to be given time to think too, and can do better if they work in pairs than work alone.


Testing Testing by itself is not as effective as remediation/feedback where the test is used to find what the student needs to improve and they then do corrective work.

Effect sizes Below 0.4, some of these add a lot of value in a short time so don’t ignore them…

Advance organizers A summary of the material in advance that puts some sort of structure to it. This can take a matter of moments and is best referred back to often.


Computer-assisted instruction Effect sizes for this are gradually rising as the instruction becomes more interactive, more engaging and generally better designed.


Instructional media Using state of the art visuals, videos, etc


Affective attributes of students The attitudes, beliefs and feelings of students


Programmed instruction A form of instruction that involves students being taught by a computer or set of workbooks, by doing a series of prescribed tasks. If the student gets an answer wrong they are directed back to correct their misunderstanding. Devised by Skinner in the 1960s, but not much used now.

Individualisation Students working on an individualised programme of learning. This may work better if students are not working in a solitary way.


Behavioural objectives Having and using objectives in the form: “The students should be able to…” immediately followed by an observable verb. For example ‘explain’ is okay because you can listen to, or read the student’s explanation. However ‘understand’ isn’t behavioural because you can’t see or read the understanding.


Retention Students who do not do well enough in one school year, being kept back to do the year again.


Beware Over-interpretation!

  • Surface learning (e.g. rote remembering without understanding) could produce high effect sizes short term for low cognitive skills such as remembering. For example the use of mnemonics has an effect size of about 0.8 (There is more to learning than passing memory tests.)
  • Most of the research was done in schools, though Hattie says effect sizes are remarkably stable and not much influenced by age
  • Some high-effect strategies are ‘Russian Dolls’ with other strategies ‘inside’.

Some low effect sizes are not very time consuming and well worth trying for their additive effect.


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