Research literature is full of research-based instructional strategies that highly effective teachers utilize on a consistent and systematic basis. And, it is well known that in multiple fields there exists a gap between what people know and what they actually do, commonly referred to as the knowing-doing gap. This study sought to examine whether this same gap exists in the field of education. In other words, this study sought to describe what high school mathematics, science, English, and social studies teachers know about effective instructional strategies and what they actually do in their classrooms. The researcher reviewed studies, books, journal articles, and other professional literature in order to identify what the most effective teachers know and ostensibly should do in their classrooms. The result was the identification of ten highly effective instructional strategies: learning objectives, accessing prior knowledge, delivery of new declarative information, delivery of new procedural information, application of new information, summarizing or generalizing, note taking, comparing similarities and differences, providing reinforcement or recognizing effort, and cooperative learning or small group work. From these ten strategies, the researcher developed a web-based survey designed to measure all ten of these strategies. High school mathematics, science, English, and social studies teachers were invited to participate in the study. From the survey three teachers expressed a desire to complete a follow-up interview and of those three, two completed the interview. The results indicated that there may be a gap between what teachers profess to know and what they actually do in their classrooms. Given these findings of what teachers know and what teachers do, the researcher recommends that teacher preparation courses, educational service units, and district level professional development focus on efforts to help close the teacher knowing-doing gap, and ultimately improve student learning. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]