The study examines whether and how the cognitive demand level of teachers' content knowledge contributes to student achievement. In the context of this study, the level of cognitive demand refers to the kind of teacher content knowledge and thinking processes required to successfully accomplish a task, in terms of knowledge of facts and procedures (level 1), knowledge of concepts and connections (level 2), or knowledge of models and generalizations (level 3). 105 middle grades mathematics teachers from a number of school districts in an urban area in the Southwestern U.S. were tested using the Teacher Knowledge Survey. The level of teachers' content knowledge was assessed and tested for correlation with student achievement in the state-mandated standardized test.