The traditional high school suffers from ineffective pedagogy, a problematic approach to proof, and a rigid separation from other parts of the secondary math curriculum. Transformational geometry can help address those limitations: it can be used to bring in new approaches to teaching, broaden, and deepen the understanding of proof, and make connections with several other parts of mathematics. Unfortunately, bringing a transformational approach to schools is hampered by a lack of clarity and the weight of tradition. Henri Picciotto will suggest some possibly useful guidelines to facilitate this transition, including what topics should be prioritized in preservice training.