Classroom Discussion: Dialogue as a Driver of Thinking

Hattie's Visible Learning Effect Size Series – #12 Classroom Discussion – Effect Size 0.82

To note: John Hattie’s Visible Learning research brings together over 1,500 meta-analyses, covering more than 90,000 studies and millions of students. Its aim is to identify what works best in education by measuring impact using 'effect size'. In this context, an effect size of 0.4 is considered average progress over a year. Anything above 0.6 is seen as highly impactful. This blog is part of a 20-post series exploring the top-ranked influences in Hattie’s Visible Learning research, with a focus on practical strategies teachers can use to make a meaningful difference.

A classroom is more than a place for delivering content. It is a space for thinking, questioning, responding, and making sense of ideas together. And one of the most effective ways to activate that thinking is through structured, purposeful discussion.

With an effect size of 0.82, Classroom Discussion is one of the most impactful tools we have. But to make it work, it needs more than just students talking. It requires clear purpose, skilled facilitation, and a culture where contributions are valued and thinking is made visible.

Done well, it transforms students from passive recipients into active participants in their own learning.

What Do We Mean by Classroom Discussion?

In Hattie’s research, classroom discussion refers to deliberate, teacher-facilitated dialogue that deepens understanding. It is not chatter, nor simply asking questions and moving on. It involves students engaging with ideas, each other’s thinking, and their own misconceptions.

Effective discussion:

• Encourages reasoning, elaboration, and justification

• Includes all students, not just the most vocal

• Supports vocabulary, metacognition, and conceptual clarity

• Centres on learning goals, not just participation

It can happen in pairs, small groups, or as a whole class, but the common thread is structure and intention.

Why It Matters

When students articulate their ideas aloud, they do more than share what they know, they process, consolidate, and refine it.

Discussion:

• Helps students clarify and rehearse their thinking

• Reveals gaps in understanding or alternative viewpoints

• Builds confidence in expressing academic language

• Encourages active listening, challenge, and reflection

It also provides teachers with valuable insight into how students are thinking, not just what they remember. That makes it a powerful formative assessment tool.

A teacher I was discussion a lesson with recently said to me: “It wasn’t until I heard my students discuss the concept that I realised what they’d misunderstood. The discussion made their thinking visible, and that changed how I taught the next lesson.”

Practical Strategies for High-Quality Discussion

1. Frame Talk with a Purpose - Before starting, share the learning intention and why talk matters for it.

   For example: “We’re going to discuss this idea to help us understand the causes behind the character’s decision.”

2. Use Talk Prompts and Sentence Starters - Structure supports inclusion. Prompts like:

   • “I agree with that because…”

   • “What do you mean by…?”

   • “Can you give an example?”
     …help students extend their responses and support respectful challenge.

3. Build Talk Time In - After modelling, ask students to discuss the question with a partner before feeding back. This encourages participation from more students and builds confidence to contribute publicly.

4. Listen for Ideas, Not Just Answers - If the focus is only on the ‘correct’ response, students may disengage. Encourage exploratory thinking and acknowledge partial ideas as stepping stones.

5. Capture Thinking Publicly - Use the board, flipchart, or a visible online tool to note key contributions. This shows that ideas are valued and creates a shared record to return to.

Quick Wins for This Week

• Try adding one sentence starter to your next discussion prompt

• Use “turn and talk” before asking for hands up

• Ask one student to summarise what another said, to build active listening

• Keep a visible note of ideas shared during class talk

Try This

Choose one upcoming lesson. Before the main activity, pose a discussion question that requires reasoning, not recall. Observe not just what students say, but who is speaking, how ideas build, and what it tells you about their understanding. Use what you hear to adapt your next step.

Challenges and Considerations

Not all students feel confident speaking aloud, and some may dominate the space while others stay silent. This is where structure matters.

Use roles, group norms, and routines to support equity of voice. Establish clear expectations about listening and respect. Sentence stems, wait time, and paired talk help level the field.

Teachers also need to feel confident letting students lead the dialogue. That requires trust in the students and in the process.

For leaders, this means valuing discussion not as a ‘nice to have’ but as a rigorous, research-informed strategy that deserves time and development.

Reflections

For teachers:

• Who is doing most of the talking in your classroom?

• How do you structure discussion so that more students are included?

• What have your students’ words recently revealed about their thinking?

For leaders:

• Do your CPD structures support teacher confidence in facilitating discussion?

• Is classroom talk visible in your learning walks and coaching conversations?

• Are students being given enough opportunities to think out loud?

Further Reading and Resources

• Oral Language Interventions – Education Endowment Foundation
  https://educationendowmentfoundation.org.uk/education-evidence/teaching-learning-toolkit/oral-language-interventions

• Accountable Talk® – Institute for Learning
  https://ifl.pitt.edu/accountable-talk/

Research Connections

• Hattie, J. (2009) – Visible Learning - Highlights Classroom Discussion as a high-impact instructional strategy (effect size 0.82) that supports deeper learning and student engagement.

• Mercer, N. & Littleton, K. (2007) – Dialogue and the Development of Children’s Thinking - Emphasises the role of talk in shaping cognition, particularly when discussion is scaffolded and purposeful.

• Alexander, R. (2017) – Towards Dialogic Teaching - Explores how dialogic approaches help students develop reasoning, reflection, and critical engagement through structured talk.

Visible Learning Blog Series

1. Stronger Together: How Collective Teacher Efficacy Unlocks Student Potential (1.57)

2. Students Knowing Themselves: How Self-Reported Grades Support Progress (1.33)

3. Judging Potential: The Power of Teacher Estimates of Achievement (1.29)

4. Supporting Every Learner: How Response to Intervention Changes Trajectories (1.29)

5. Teaching for Thinking: Why Piagetian Programs Make a Difference (1.28)

6. From Misconception to Mastery: How Conceptual Change Programs Support Deep Learning (0.99)

7. Knowing Where to Start: Why Understanding Prior Knowledge Enables Effective Teaching (0.94)

8. Making It Stick: Why Connecting New Learning to What Students Already Know Matters (0.93)

9. Belief Before Progress: Why Self-Efficacy Is a Game-Changer for Learning (0.92)

10. The Trust to Teach: Why Teacher Credibility Drives Student Engagement (0.90)

11. Micro-Teaching: How Short Reflections Make a Big Difference (0.88)

12. Classroom Discussion: Dialogue as a Driver of Thinking (0.82) — You are here

13. Targeted Support: What Works for Learners with Additional Needs

14. Relationships That Matter: How Teacher-Student Connection Fuels Learning

15. Revisiting and Remembering: Why Spaced Practice Outperforms Cramming

16. Learning to Learn: Embedding Meta-Cognitive Strategies Across the Curriculum

17. Stretching Forward: What Acceleration Means in Practice

18. Calm and Clear: How Classroom Management Enables Progress

19. Word Power: Why Vocabulary Programs Widen Access

20. Read It Again: How Repeated Reading Builds Fluency and Confidence

Next up: Targeted Support - exploring how strategic interventions for students with additional needs can close gaps, build confidence, and reconnect learners to the heart of classroom learning.