Although institutional recognition of high school psychology is fairly recent, psychology and psychological subject matters have a history dating to at least the 1830s. By the middle of the twentieth century, high school psychology courses existed in nearly all U.S. states, and enrollments grew throughout the second half of the century. However, courses were usually elective, and most teachers lacked degrees in psychology. Studies in the latter half of the twentieth century suggested that high school psychology courses did little to prepare students for college-level psychology, probably because the high school classes often did not include core subject matters of psychological science. However, the 1990s brought several landmark developments for high school psychology, including establishment of Teachers of Psychology in Secondary Schools (TOPPS), a number of university-sponsored institutes providing professional development for teachers, and inauguration of the Advanced Placement (AP) Psychology program. Today, high school psychology teachers enjoy increased recognition within the American Psychological Association (APA), availability of significant teaching resources, and national standards to guide course development. A million students annually take high school psychology, with about a quarter million taking the AP Psychology exam. The course is now recognized as an important first exposure to psychological science.