High school social studies students (n=448) were each assigned to one of 16 groups defined by possible combinations of two teacher uncertainty conditions (uncertainty vs. no uncertainty), two teacher "bluffing" conditions (bluffing vs. no bluffing), two lesson discontinuity conditions (discontinuity vs. no discontinuity), and two lecture notes conditions (notes handouts vs. no notes handouts). Each group was presented a lesson about the geography, politics, history, and economy of the country of Botswana. The lessons were the same except for variations in the four conditions stated above. After the lesson, each group was tested on comprehension of the material, and then each group completed a lesson evaluation. Teacher uncertainty negatively affected achievement, and notes handouts positively affected achievement. Both teacher bluffing and lesson discontinuity negatively affected student evaluation of the lesson. Several significant interactions were obtained. These findings are discussed in relation to previous research on low-inference behaviors related to teacher clarity. (Author)