Project THISTLE: Thinking Skills in Teaching and Learning was designed to improve both the reflective thinking capabilities of urban high school students and their pre-college preparation. This study was conducted to elicit teacher perceptions of factors inhibiting reflective thinking in schools. Most important among the perceived constraints on reflective thinking in schools were student lack of prior experience; curricular pressures; and lack of stress on reflective thinking in statements of school philosophy, teacher education programs, and the curriculum. Urban, as compared with suburban, teachers reported less stress on reflective thinking in statements of school philosophy, less teacher autonomy, and lower levels of basic skills and background knowledge among both teachers and students. Teachers believe administrators value quiet and order over reflective thinking. The major factors identified in a factor analysis of teacher responses included teacher responsibility, student expectations, student readiness, curriculum, supervisor responsibility, and teacher insecurity. (Author/DWH)