This chapter traces the origins of the Reframing Mathematical Futures II (rmfii) research project before describing how rich assessment tasks and Rasch analysis techniques were used to develop an evidence-based resource to support the teaching and learning of algebraic, statistical and geometric reasoning in Years (i.e., Grades) 7 to 10. Hypothesised learning progressions were developed for each of the three target domains based on prior research. Potential assessment tasks, together with detailed scoring rubrics, that addressed the learning progressions were developed and trialed. A detailed examination of the Rasch analysis output indicated modifications that were needed and the modified questions were retrialed. Finally, the resulting variable was interpreted and segmented into Zones that were used as the basis for developing teaching advice. In describing this process, we comment on the application of learning trajectories more generally and suggest further avenues for research in this field.