Teacher Coaching: The History, Impact, and Potential
Teacher coaching is now woven into the fabric of professional learning in schools. Literacy coaches, instructional coaches, peer coaches, academic coaches—most educators have worked with one, and many rely on coaching as a primary source of support. Yet despite its prevalence, coaching’s average impact on student learning remains modest. The Visible Learning research places coaching at an effect size of 0.25, well below the 0.40 hinge point that signals accelerated learning.
That number often surprises educators. Coaching feels powerful. It feels meaningful. It feels like it should make a difference.
And it can. As we have stated, “coaching has the potential to be one of the most powerful ways we can support teachers… but coaching doesn’t always make a difference.”
Understanding why—and what we can do about it—is essential if coaching is going to fulfill its potential.
How We Got Here: Coaching’s Evolution From Supervision to Partnership
Coaching didn’t begin as coaching. Its earliest roots trace back to the 1960s, when “clinical supervision” was the dominant model for supporting teachers. This approach introduced structured pre‑observation conversations, classroom visits, and reflective post‑observation dialogue. It was intentionally developmental rather than evaluative—a significant shift at the time.
These early practices planted the seeds for what coaching would become: a process grounded in reflection, inquiry, and professional trust.
By the 1980s and 1990s, coaching began to take shape through two influential models:
Cognitive Coaching℠, which positioned teachers as self-directed learners and emphasized intentional questioning to strengthen decision-making.
Peer coaching, which demonstrated that professional learning “sticks” when teachers collaborate, observe one another, and debrief their practice.
These models established a foundational truth: coaching is not supervision. It is not evaluation. It is partnership.
The 2000s brought instructional coaching to scale. Coaching became more formalized, more widespread, and more tied to accountability. By the 2010s, coaching diversified—math coaches, multilingual learner coaches, technology coaches, special education coaches. Coaching became essential professional learning.
And yet, despite this evolution, the impact remained inconsistent.
Why Coaching’s Impact Has Been Limited
We have identified several realities that help explain why coaching has not yet reached its full potential.
1. Coaching is often invitational.
In many schools, coaching is optional. Teachers can choose whether to participate, how deeply to engage, and whether to implement new ideas. This voluntary approach has benefits—coaching thrives when teachers are open and willing—but it also has limitations. As we have noted, “the very teachers who might benefit most may opt out.”
When participation varies, impact varies.
2. Implementation is inconsistent.
Even when teachers participate, there is no guarantee that strategies will be applied consistently. Trying a practice once is not the same as integrating it into daily instruction. Coaches can model, encourage, and support, but implementation ultimately rests with the teacher.
This gap between conversation and classroom practice helps explain why coaching sometimes shows modest effects on student learning.
3. Some coaching models are outdated.
Coaching has evolved, but not all coaching practices have kept pace with contemporary research or classroom realities. Some models were designed for contexts that no longer exist. Others rely heavily on compliance rather than collaboration.
When coaching models don’t align with current evidence, their impact is limited.
4. Coaching is an indirect influence.
Coaching strengthens instruction, but it does not directly teach students. Its impact is mediated through teacher practice—which varies widely across classrooms, grade levels, and contexts.
This doesn’t diminish coaching’s value. It simply clarifies the challenge: coaching must be strong enough to influence what teachers actually do.
The Untapped Power of Coaching
The effect size of 0.25 does not tell the whole story. In fact, it may underestimate coaching’s true potential.
Coaching amplifies high-impact practices.
Many of the highest-effect-size strategies—teacher clarity (0.85), feedback (0.70), formative evaluation (0.77)—are strengthened through coaching. Teachers often know about these practices but struggle to implement them consistently. Coaching provides the support needed to bring them to life.
Coaching improves instructional quality.
Research consistently shows that coaching strengthens teaching practice, even if the direct effect on student achievement is smaller. Improvements in instruction are not trivial—they are foundational.
Coaching builds professional culture.
Coaching reduces isolation, increases collaboration, and fosters shared accountability for student learning. These cultural benefits are difficult to quantify but essential for sustained improvement.
“Teaching is complex work, and no one should have to navigate it in isolation.” Coaching creates the structures and relationships that make continuous learning possible.
Where Coaching Goes From Here
The history of coaching shows a clear shift—from evaluation and compliance toward trust, reflection, and collaboration. But the next era of coaching requires something more: credibility, clarity, and actionable support.
To fulfill its potential, coaching must:
Build trust through rapport, respect, and confidentiality
Use evidence neutrally to ground conversations in clarity rather than judgment
Guide thinking through purposeful dialogue that strengthens decision-making
Provide actionable next steps teachers can implement immediately
Focus relentlessly on student learning as the ultimate goal
Coaching is not a program. It is not a checklist. It is not a script.
Coaching is a relationship. Coaching is a conversation. Coaching is a shared commitment to growth.
And when done well, coaching becomes one of the most powerful forces for professional learning in schools.
The Bottom Line
Coaching’s impact is not limited—it is latent. The potential is there. The research is clear. The challenge now is to deepen the quality of coaching so it consistently delivers the growth teachers deserve and the learning students need.
As the authors remind us, “coaching is the art and science of shared growth.”
That shared growth is exactly where the next chapter of coaching begins.