This report explains the growing evidence that investments in teacher knowledge are among the most productive means for increasing student learning. The creation of rigorous professional standards for teachers is one sign of progress in this area. However, new teaching standards will have little import for students, particularly the most vulnerable ones, if school districts continue to hire teachers who are unprepared and assign many teachers outside their fields of expertise. The report discusses whether it is possible to raise standards and have enough teachers. It describes recruitment initiatives to address the problems of teacher supply, demand, and the need to achieve greater equity in all students' access to high-quality teaching. It also examines variations in standards across states and discusses what states and school districts can do to raise teacher standards while equalizing teacher salaries, establish license reciprocity across states, and expand teacher education programs in high-needs fields. The report offers action steps for governors and state legislators as well as state boards of education, state education agencies, and professional standards boards. An appendix presents the basis for cost and attrition estimates. (Contains 10 charts and 28 references.) (SM)