Response from W. David Tilly, Ph.D.: Response to Intervention (RtI) is most accurately described as a movement rather than a thing. For the past 30 years or so, a fairly tight knit group of people across the country have been quietly working on ways to bring evidence-based practice into schools. There have been a number of iterations in that direction. Some of the earliest roots of what is now known as RtI can be found in practices such as precision teaching (Ogden Lindsley), direct instruction (Zig Engelmann and Wes Becker), behavioral consultation (John Bergan), and curriculum-based measurement (Stan Deno). All of these approaches and initiatives have concerned themselves with improving instruction for students in measurable ways, using objective growth of student skills as the criterion of effectiveness. Many different implementations of evidence-based practice have been tried in many parts of the country, with varying degrees of success—and many important lessons were learned. The people involved with these implementations were both researchers and practitioners, but they shared one characteristic. They were intensely interested in not only figuring out "what works" but also "how to make it work" in the real world of schools. As time went by, we got better and better at improving results for students until something of a perfect storm occurred:

1. We had data showing that despite our best efforts, many students still were not benefiting sufficiently from their school experience.
2. The world became globalized and if the United States is to remain competitive, nearly all of our students are going to have to achieve at much higher levels.
3. The accountability movement in the United States (led primarily by the No Child Left Behind Act of 2002) was forcing schools to pay much more attention to the achievement of all of their students. At the same time, funding for education was at best flat.

So there was this huge quest to figure out how to become both more efficient and more effective across the board in schools. Into this vacuum entered what is now called RtI. Stated plainly, RtI results from the marriage of a long history of evidence-based practices (and the lessons learned there from) with a new and more efficient resource-deployment system (the Three-Tier Approach) that better allows schools to match instructional resources directly to the nature and intensity of student learning needs. Fancy sounding words that basically mean that RtI lets schools look at kids' needs and use their resources most efficiently to provide effective instruction for all of them.

In short, schools that are effective do three things well:

1. They figure out what they want kids to know and be able to do.
2. They align their curriculum and instruction to teach those things.
3. They keep score.

RtI provides the evidence-based tools to help schools do these things efficiently. So where does RtI come from? It comes from the confluence of a long history of applied research and practice coupled with improved engineering for delivering instruction in the real world, all wrapped up in the perfect storm of political and social policy imperatives demanding better outcomes for all of our children. Put that all together with a big dose of common sense and you get RtI.