Quality education is imperative in preparing students in the United States to succeed in a competitive and ever-changing global society. Critical thinking, an essential component of a quality educational program, has been identified as a key 21st Century skill. However, research indicates a gap in educational preparedness between high school and college, particularly in the teaching of critical thinking skills. This study investigated the emphasis that South Dakota English content instructors placed on the teaching of critical thinking skills at the high school junior and senior level and at the college freshmen and sophomore level by examining instructors' perceptions. A survey was developed to obtain information concerning the importance of teaching critical thinking skills, preparation for teaching critical thinking skills, and obstacles to teaching critical thinking skills. The study further examined the differences in perceptions that existed based on years of teaching experience, highest degree earned, level of teaching, and average class size. Instructors who participated in the study strongly believed incorporating critical thinking skills is important and felt confident in their abilities to teach those skills. As a result, South Dakota public high school junior/senior and college freshmen/sophomore English content instructors incorporate critical thinking into their lessons. Those instructors with teaching experience generally believed they had received training in the teaching of critical thinking skills during their teacher education programs to a greater extent than those with limited teaching experience, and instructors generally had been actively involved in professional development in the last two years, increasing their abilities to teach critical thinking skills. However, fewer respondents indicated they were provided feedback on their ability to teach critical thinking skills as a result of performance evaluations. Instructors varied in their beliefs concerning obstacles to teaching critical thinking skills. High school junior/senior English instructors believed class size, pressure to improve scores on standardized tests, and lack of planning time to be the greatest obstacles, whereas college freshmen/sophomore English instructors identified lack of knowledge or understanding of critical thinking, class size, and limited professional development opportunities in critical thinking as the greatest obstacles. [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.]