Problem posing, the process of formulating problems based on a given situation, is an essential practice in mathematics and other disciplines. Although this is acknowledged in policy documents, problem posing is neither substantively nor consistently included in the school mathematics curriculum. In this paper, we first comment on the state of problem posing in school mathematics and discuss three recommendations to improve its integration into curriculum materials and classroom practice. These recommendations present a low barrier to entry for teachers and students and require only minor changes to common mathematics classroom activities and curriculum materials. Based on the three recommendations, as well as the features of effective teacher professional development, a program was created to investigate longitudinally the impact of problem-posing professional development on teachers' conceptions of problem posing and their design of lessons to teach mathematics using problem posing, as well as on students' learning. Initial findings are presented, including the significant changes in teachers' conceptions of problem posing and teachers' design of lessons to teach mathematics using problem posing, as well as the impact on students' learning.