This chapter summarizes some of the findings and recommendations of the National Research Committee (NRC) on Test Design for K-12 Science Achievement and is based on the committee’s final, book-length Report—Systems for State Science Assessment (NRC 2006). While the committee’s report is targeted at state policy and education decision makers, many of the findings are of interest to teachers and others involved in the improvement of science education and assessment in their states. In this chapter, the authors try to connect a few of the committee’s findings and recommendations to issues of interest to teachers.