The PISA results also suggest the importance of curriculum. In countries such as Finland and Korea, there is a universal curriculum; students of the same age study the same subjects in the entire country. In the United States, each state determines its own curriculum. Perhaps because the fifty states decide on their own curricula , some U.S. states rank very high on the PISA exams, and some rank low. The word curriculum refers not only to the courses that students take but also to all of the topics in each course. In countries that do well on the PISA exam, a typical 8th grade course focuses on 10-15 topics. In the United State, an 8th grade course typically includes 35 topics. Perhaps this is too many.