This study evaluated a multi-year collaborative project between elementary public schools in one district and university researchers. While the district wanted to improve elementary grades students' achievement in mathematics, they did not want teachers to adopt an instructional approach where they focused primarily on test-defined content. Using principles from Cognitively Guided Instruction, the partnership focused on promoting teachers' understanding of mathematical thinking, as it was demonstrated by students, while they completed authentic activities. The authors used cultural-historical activity theory (CHAT) to evaluate how school administrators' evolving expectations for students' achievement influenced opportunities for teachers and the university faculty member to demonstrate more dynamic notions of students' expertise and knowledge.