Effect size in education research and practice

Teaching strategies

Effect size in education research and practice

A guide for classroom teachers and teacher aides

Effect size – the impact that a particular strategy, technique, circumstance or issue has on student learning.

Emply lecture room.

Effect size (in terms of teaching strategies) refers to the impact that a particular strategy, technique, circumstance or issue has on student learning (or other factor under measurement). When something has an impact on learning, the effect can be measured and expressed as a number. Simplistically speaking, this allows 2 separate effects to be compared in a way that makes sense to the average person with no statistical training. The measurement number is usually between 0 and 1 but it can also be as high as 2 or even be negative. A common rule of thumb is that an effect of 0.2 or higher is small (but still an effect nonetheless), 0.5 or higher is a medium effect and 0.8 and higher a very strong effect.i

When something has an impact on learning, the effect can be measured and expressed as a number.

It should be noted that due to the way effect size is calculated, comparing 2 effects in terms of the actual measurable improvements in the classroom is not as simple as comparing the 2 numbers. For example, an effect of 0.4 is not double the effect of 0.2 (in percentage terms, the actual difference is about 5% when calculated by the common language effects method, or CLE). There are also issues with comparing effect sizes that are calculated based on very different studies and contexts (for example, comparing the effect of a 20-year-old study of 5 participants from New Zealand with a recent study of 100,000 schools in the US is not a fair or valid comparison).

Another point to note is that a low effect size does not mean that a strategy is worthless or any less effective than a strategy with a higher effect size. For example, individualised instruction has a relatively low effect size of 0.29 in the table below, but that does not mean schools should simply abolish individualised instruction. What effect size does tell us is that strategies and influences with a known higher effect size should be regularly considered for implementation (when appropriate and relevant). It is very likely that these identified strategies will have a positive impact on learning. Effect size is a powerful tool for understanding what strategies are likely to have the biggest impact on the learning process and student achievement.

John Hattie is by far the most prominent and well-known academic in terms of effect-size work. Hattie collated hundreds of studies and has formulated a list of over 250 effect sizes. The table below shows a snapshot of some of the influences collected and synthesised by Hattie and how they relate to the strategies and skills found in this book. The selected influences are in descending order in terms of their effect size. While there are criticisms of Hattie’s work, this list provides a simple reference to remind us of what high-quality teaching looks like.ii

(From Hatti)

Example strategies
(From this book)

Teacher estimates of achievement Setting goals, backwards design and designing down
Response to intervention Intervention, remedial instruction, one-on-one instruction
Self-efficacy Coping, motivation, metacognitive skills
Classroom discussion Discussions, pair and group work, debates
Scaffolding Scaffolding, zone of proximal development, guided and shared learning
Deliberate practice Deliberate practice, spaced learning, overlearning
Summarisation Summarise and synthesise, compare and contrast
Effort Motivation, metacognitive skills, active reading
Planning and prediction Prediction, using cues
Repeated reading programs Repeated reading, active reading
Teacher clarity Explicit instruction, questioning techniques, rapport building
Reciprocal teaching Learning by teaching, peer modelling, peer tutoring
Rehearsal and memorisation Rehearsals, spaced learning, deliberate practice
Instructional programs Explicit instruction, repeated reading
Phonics instruction Phonics
Feedback Feedback techniques, rapport building, formative assessment
Deep motivation and approach Motivation, rapport building, setting goals
Concept mapping Graphic organisers, prediction, metacognitive skills
Metacognitive strategies Metacognitive skills, setting goals, transferable skills
Spaced vs. mass practise Spaced learning, massed practice, deliberate practice
Direct instruction Explicit instruction, repeated reading
Mastery learning Mastery learning, overlearning
Explicit teaching strategies Explicit instruction, metacognitive skills, formative assessment
Self-verbalisation and self-questioning Self-questioning, mental scripting, metacognitive skills
Peer tutoring Peer tutoring, peer questioning, peer modelling
Teacher-student relationships Rapport building, formative assessment, feedback techniques
Self-regulation strategies Metacognitive skills, coping
Parental involvement Homework, flipped learning
Clear goal intentions Setting goals, backwards design and designing down
Formative evaluation Formative assessment, feedback techniques, rapport building
Questioning Questioning techniques, explicit instruction, feedback techniques
Comprehension programs Active reading, prediction
Integrated curricula programs Cross-curriculum learning, team teaching
Small group learning Pair and group work, peer tutoring
Study skills Metacognitive skills, coping
Writing programs Remedial instruction, intervention, writing to learn
Imagery Visualisation, using cues, prediction, active reading
Worked examples Explicit instruction, scaffolding, guided and shared learning
Student-centred teaching Pair and group work, peer tutoring
Matching style of learning Learning styles, multiple intelligences
Online and digital tools Online learning, blended learning, technology learning
Homework Homework, flipped learning
Problem-based learning Problem-based learning
Grit/incremental vs. entity thinking Metacognitive skills, setting goals
Individualised instruction One-on-one instruction, intervention
Co-(or team) teaching Team teaching

Foot notes:

  1. Cohen, J. (1988). Statistical power analysis for the behavioral sciences (2nd ed.). Hillsdale, NJ: Lawrence Earlbaum Associates.
  2. See either: Hattie, J. (2009). Visible Learning. New York: Routledge, Taylor & Francis Group, or the website: visible-learning.org for the full list. Also note other well-known sources including the What Works Clearinghouse found at https://ies.ed.gov/ncee/wwc/.

About the author

Image of the managing director of ITAC.


Adam Green is an advisor to government, a registered teacher, an instructional designer and a #1 best selling author. He is completing a Doctor of Education and was previously head of department for one of the country’s largest SAER (students at educational risk) schools. Adam is managing director of ITAC, an accredited training provider for thousands of teacher aides every year.

Source: Teaching Skills and Strategies for the Modern Classroom: 100+ research-based strategies for both novice and experienced practitioners. Amazon #1 best seller in the category of Classroom Management.

Disclaimer: While every effort has been made to check his article for accuracy, information may be outdated, inaccurate or not relevant to you and your location/employer/contract. It is not intended as legal or professional advice. Users should seek expert advice such as by contacting the relevant education department, should make their own enquiries, and should not rely on any of the information provided.


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