Mathematical Proficiency cannot be categorised as present or absent, one needs to keep in mind that every mathematical idea can be understood in many levels and many ways (National Research Council, 2001). It is something that is acquired over time and as students move through their schooling they should become increasingly proficient. Therefore, to become proficient, students need to spend time doing mathematics (solving problems, justifying their thinking, developing understanding, practicing skills) and building connections between their previous knowledge and new knowledge. How do we do this? Using the Mathematical Proficiency Strands, this workshop will evaluate an instructional model in teaching Problem Solving, the strategies students need, the tasks we select, how to enable and extend and how students can model their thinking. Participants will also explore how we assess the proficiency strands through whole school moderation practices and the use of rubrics for self, peer and teacher feedback.