The new "Mathematics Framework for California Public Schools" identifies complex instructional activities and student performance, and requires new assessment methods to reveal that performance. One of the goals of the California Assessment Collaborative (CAC) is to study the effects of local assessment development and implementation efforts on teaching and learning. This report describes how one local CAC mathematics assessment initiative connects with the statewide curriculum reform and impacts what occurs in the classroom. The Mt. Diablo Curriculum-Based Alternative Assessment of Mathematics (CBAAM) was the program examined through interviews of 59 third-grade teachers. Their responses made it clear that the CBAAM had profound short-term effects on teaching and learning. Teachers resequenced content, introduced new content, and emphasized instructional processes as a result of the CBAAM. Evidence also suggests that there will be substantial long-term impact. Two tables present study findings. Two appendixes supplement the report with a student booklet from the 1994 Curriculum-Based Alternative Assessment of Math, the third grade survey letter, and interview guiding questions. (Contains 18 references.) (SLD)