Responsiveness-to-intervention: a decade later.

In this introduction to this special issue, "A Decade Later," we provide an overview of the accomplishments as well as the persistent questions surrounding RTI. We organize this discussion within 3 categories: assessment, instruction, and policy. Within each of these sections, we also highlight how the articles in the present special issue expand upon the key issues. Developed initially for the early grades (kindergarten through third grade) and primarily in the area of reading, many-although not all-of these issues speak to the expansion of RTI to address a broader set of academic content areas and the full range of grade levels.