This summer I visited East Point Lighthouse on the red shoreline of Prince Edward Island, it was here that I heard the remarkable story of how the entire towering structure was picked up using a capstan and horses, then moved 487 metres east in 1885. The reason? Nautical charts showed the light at the tip of the point, but in fact it had been built inland. So after the wreck of HMS Phoenix in 1882, locals recognised that fidelity to the map mattered dangerously. The move was a deliberate act of aligning position with purpose, of restoring integrity so that the warning light could do its job, an apt metaphor for what fidelity demands.
The word fidelity has its roots in faithfulness. In education, it is often used to describe the extent to which a practice, strategy, or programme is delivered in the way it was originally intended, with best practice and research in mind. Fidelity matters because ideas rarely fail in their conception; they falter in their translation into classrooms. The Education Endowment Foundation’s (EEF) Guidance Report on Implementation reminds us that implementation is a process, not an event. Without fidelity to core principles, even the most robust evidence-based practices can fracture when they encounter the complexity of school life.
Fidelity is not about slavish compliance or rigid adherence. Instead, it is about holding true to the underlying mechanisms that make an approach effective, while recognising that contextual adaptation is inevitable. This tension between faithfulness and flexibility lies at the heart of great teaching. Get it wrong, and we risk what Rob Coe memorably called lethal mutations: well-intentioned adaptations that erode the original purpose of a strategy until it ceases to be effective.
The promise and peril of implementation
Dylan Wiliam has long argued that “everything works somewhere, nothing works everywhere.” This insight captures the delicate balance leaders must strike when introducing new practices. Research gives us promising approaches, but it is fidelity in the implementation phase that determines whether those approaches thrive or wither in a specific school. The EEF Implementation Guidance urges leaders to treat implementation as a staged process: explore, prepare, deliver, and sustain. Each stage requires fidelity to intent, careful monitoring of practice, and a willingness to adapt without losing sight of the core.
The danger arises when adaptations strip away the very features that made a strategy effective. Rob Coe’s idea of lethal mutations helps us diagnose this phenomenon. A school adopts retrieval practice but turns it into low-level quizzes disconnected from curriculum thinking. A department embraces feedback but dilutes it into time-consuming marking that neither informs learning nor empowers students. The label remains, but the impact is lost. Fidelity requires us to protect the “active ingredients” while avoiding the allure of superficial adoption.
Fidelity and the craft of teaching
Fidelity should never be confused with uniformity. Tom Sherrington captures this in his work on WalkThrus, noting that clear models of practice offer teachers a shared language and reference point, but professional judgment remains vital. A WalkThru is a scaffold, not a straitjacket. Teachers apply it with nuance, drawing on their subject expertise, their knowledge of students, and their understanding of context.
Here lies the paradox. Fidelity demands consistency to principles, but teaching is irreducibly complex and contingent. The solution is to identify what must remain fixed, the “non-negotiables” grounded in evidence and what can be flexed by professional judgement. For example, fidelity to formative assessment means that teachers systematically elicit evidence of learning and act upon it. How they do so, whether through quizzes, mini-whiteboards, diagnostic hinge questions or elaboration, depends on their context, like subject and learners. Fidelity, then, is to the principle, not the performance.
Leadership, culture, and fidelity
Fidelity is as much a leadership challenge as a classroom one. Leaders who treat implementation as a checklist often find themselves disappointed when the practice fails to take root. Fidelity grows in cultures where professional learning is ongoing, dialogue is open, and teachers feel ownership.
Viviane Robinson’s work is particularly instructive here. Robinson underscores the importance of trust and relational leadership. Fidelity cannot be sustained through surveillance or compliance; it grows when teachers feel that leaders respect their professionalism. By engaging with staff as co-learners and collaborators, leaders create the conditions for authentic buy-in. This is where distributive leadership matters. When middle leaders are empowered to interpret strategy, adapt it intelligently, and lead grassroots dialogue, fidelity ceases to be a top-down mandate and becomes a shared endeavour.
Grassroots leadership protects against lethal mutations because it multiplies the number of people who understand the why behind a practice. Instead of a single senior leader policing fidelity, dozens of middle leaders can nurture it daily in conversations, planning meetings, and departmental reviews. Robinson’s research shows that this form of distributive leadership, rooted in expertise and trust, ensures that fidelity becomes part of the school culture rather than an external demand.
Fidelity, innovation, and sustainability
It is tempting to see fidelity as the enemy of innovation, but the opposite is true. When schools commit to fidelity in implementation, they create the conditions for innovation to flourish responsibly. By embedding new practices with integrity, teachers gain the confidence and clarity to make thoughtful adaptations, rather than reactive or superficial ones.
Improvement comes not from chasing novelty, but from sustained practice. Fidelity ensures that we give ideas the time and stability they need to mature, rather than discarding them prematurely. In doing so, we reduce initiative fatigue, protect teacher workload, and build cumulative gains.
Sustainability also depends on fidelity. Initiatives often collapse when the original champions move on because the practice has not been embedded with enough clarity or coherence. Leaders who build fidelity into school systems through professional learning, coaching, shared resources, and aligned QA processes ensure that practices survive personnel changes and remain part of the school’s DNA.
Fidelity in teaching and learning is about more than faithful delivery; it is about protecting the core principles that make strategies work, while allowing for intelligent adaptation. It is about resisting lethal mutations, ensuring that good ideas do not deteriorate into hollow rituals. It is about leaders treating implementation as an ongoing process, not a one-off event, and teachers applying evidence with professional judgment.
Above all, fidelity is an act of professional faith. It is about staying loyal to the principles of effective teaching, even as we adapt them to the needs of our students. In a landscape crowded with initiatives, fidelity helps us discern the signal from the noise. It is the difference between surface adoption and deep impact.
References
Coe, R. (2013). Improving Education: A Triumph of Hope over Experience. Centre for Evaluation and Monitoring, Durham University.
Education Endowment Foundation (2019). Putting Evidence to Work: A School’s Guide to Implementation. London: EEF.
Robinson, V. M. J. (2011). Student-Centred Leadership. San Francisco: Jossey-Bass.
Sherrington, T. & Caviglioli, O. (2020). WalkThrus: 5-Step Guides to Instructional Coaching. Woodbridge: John Catt.Wiliam, D. (2016). Leadership for Teacher Learning: Creating a Culture Where All Teachers Improve So That All Students Succeed. West Palm Beach: Learning Sciences International.