Despite costly global efforts to improve and reward teacher qualifications like education and experience, little international evidence exists on the relationship between these attributes and student achievement. It is also unclear whether these attributes are more important for disadvantaged children, or in lower-income countries. This article examines the relationships among teacher characteristics (experience, education, readiness to teach, and gender), student background, and fourth grade students' mathematics and science achievement across 25 diverse countries participating in the 2003 Trends in International Mathematics and Science Study. The analysis revealed limited evidence that the teacher characteristics deemed important in teacher upgrading and compensation are systematically related to student test scores, or that these characteristics are more important for lower-income students. It also found no relationship between national income and the importance of these characteristics. These results add to increasing evidence that efforts to improve teacher quality must look beyond simply increasing and rewarding measurable teacher qualifications like education and experience. Further, those who design cross-national studies should consider developing richer measures of teacher skill and knowledge.