By definition, online learning is part of any blended learning classroom. It is the key innovation for enabling student-centered learning at scale. Given this fact, it’s easy to get caught up in thinking of technology—devices and software—as blended learnings’ core, defining feature. Yet the most powerful and important element in blended learning doesn’t have a touch screen, fancy graphics, or artificial intelligence; it isn’t built by engineers or computer scientists; and you can’t buy it online. The most important element in blended learning is one that’s been in classrooms for centuries. That element is teachers.

To illustrate this point clearly, consider how technology and teachers stack up on John Hattie’s rankings. Hattie synthesized the results of nearly 1,200 meta-analysis studies to compare various influences on student learning based on their statistically-measured effect size. When we look at hardware and software, their impact on student achievement tends to be moderate, in the rage of 0.1 to 0.6.

  • Technology with learning needs students – 0.57
  • Technology in other subjects – 0.55
  • Interactive video methods – 0.54
  • Intelligent tutoring systems – 0.48
  • Information communications technology – 0.47
  • Technology with elementary students – 0.44
  • Technology in writing – 0.42
  • Gaming/simulations – 0.35
  • Technology in mathematics – 0.33
  • Technology with high school students – 0.3
  • Online and digital tools – 0.29
  • Technology in reading/literacy – 0.29
  • Technology in science – 0.23
  • Technology in small groups – 0.21
  • Web-based learning – 0.18
  • One-on-one laptops – 0.16

Pure technology, however, isn’t the only way to influence student learning within a blended model. Online learning also gives teachers new options for how they group students, provide feedback, and use instructional time. In other words, the real potential of online learning comes not from the tools themselves, but from what the teacher’s can do using their toolbelt. When we look at many of the “offline” activities that online learning makes possible—such as small group instruction and mastery-based learning—we see even more favorable effects, ranging from around 0.3 to 0.9.

  • Micro-teaching/video review of lessons – 0.88
  • Classroom discussion – 0.82
  • Deliberate practice – 0.79
  • Interventions for students with learning needs – 0.77
  • Mastery learning – 0.57
  • Providing formative evaluation – 0.48
  • Small group learning – 0.47
  • Student-centered teaching – 0.36

Now consider teachers. Even with the best technology has to offer, teachers still stand out as more important than any other element of blended learning, with effect sizes ranging from about 0.4 to nearly 1.6: 

  • Collective teacher efficacy – 1.57
  • Teacher estimates of achievement – 1.29
  • Teacher credibility – 0.9
  • Teacher clarity – 0.75
  • Teacher expectations – 0.43

Why the focus on tech, not teachers?

Although teachers are clearly the biggest impact lever in blended learning, it’s easy to understand why technology often steals the limelight. For one, it’s much harder to recruit, develop, and support effective teachers than it is to buy new devices or software licenses; and when you walk into a classroom, new shiny hardware and flashy software are more eye-catching than the skills and expertise living inside a teacher’s mind. Thus, education leaders are easily drawn to the electronic aspects of blended learning at the neglect of the real engines of success. Additionally, blended learning and quality teaching can often seem like distinct and separate initiatives. On the landscape of education reforms, blended learning and teacher quality each has its own set of policy proponents, technical support organizations, publications, and conferences.

Yet despite the false dichotomy often drawn between improving schools through excellent teaching and improving schools through technology, teacher quality and online learning are not isolated and independent variables. Rather, they are complementary components of an effective blended learning system.

The missing measures

What doesn’t show up clearly in Hattie’s rankings are the positive interaction effects between teacher effectiveness, online learning, and the personalized learning practices that blended learning enables. While technology facilitates differentiated instruction, accelerates real-time feedback, and enables mastery-based learning, teachers often help students find their “why.” Teachers have the power to motivate and inspire students to engage deeply with educational content; they can provide students with the expert feedback to validate the meaning of their achievements; and they can show students that someone cares about their success.

For example, if we compare high-quality blended learning to the design of a high-end car, you might say teachers are like the engine and online learning is like the transmission. Just as a transmission unlocks a car’s potential for speed (imagine trying to merge onto the freeway with only first gear) online learning can enable teachers to do a host of things that are practically impossible to do by hand. But just as a car goes nowhere without the power of an engine, online learning often has little effect without teachers.

This principle bears out in practice. Many of the strongest blended-learning schools make high-quality teaching a priority, and recent reports on effective blended-learning implementation emphasize teacher development as a key to success. Additionally, a number of the leading innovators in blended learning are also experimenting with new staffing arrangements for extending the impact of great teachers.

During teacher appreciation week, we pay tribute to the original and most important educational element in any classroom: excellent teachers. And as schools experiment and iterate on their blended-learning models, we remind them that their best path to success will be through using technology as a catalyst to amplify the impact of teachers.


  • Thomas Arnett
    Thomas Arnett

    Thomas Arnett is a senior research fellow for the Clayton Christensen Institute. His work focuses on using the Theory of Disruptive Innovation to study innovative instructional models and their potential to scale student-centered learning in K–12 education. He also studies demand for innovative resources and practices across the K–12 education system using the Jobs to Be Done Theory.