Each of 20 high school algebra teachers taught a lesson on direct variation to one first-year algebra class. The students (N=455) had not previously been taught this topic in class. Before the lessons were taught, each teacher was given a list of lesson objectives. Immediately after each lesson, a posttest that focused on the lesson objectives was administered. The teachers were not shown the posttest before they taught their lessons. Correlations were found between the mean posttest scores for the classes and several variables pertaining to teacher discourse.