Even as research has begun to document that teachers matter, there is less certainty about what attributes of teachers make the most difference in raising student achievement. Numerous studies have estimated the relationship between teachers' characteristics, such as work experience and academic performance, and their value-added to student achievement; but, few have explored whether instructional practices predict student test score gains. In this study, we ask what classroom practices, if any, differentiate teachers with high impact on student achievement in middle school English Language Arts from those with lower impact. In so doing, the study also explores to what extent value-added measures signal differences in instructional quality. Even with the small sample used in our analysis, we find consistent evidence that high value-added teachers have a different profile of instructional practices than do low value-added teachers. Teachers in the fourth (top) quartile according to value-added scores score higher than second-quartile teachers on all 16 elements of instruction that we measured, and the differences are statistically significant for a subset of practices including explicit strategy instruction.