A study provided students with relevant background knowledge and tested the effects of this knowledge on two versions of a text. The two text versions were four original segments of text from a fifth-grade social studies textbook about the period leading to the American Revolution and their revised versions from an article in "Reading Research Quarterly." The revisions, which were designed to improve text coherence, resulted in improved comprehension. Subjects, 48 fifth graders, were presented with an instructional module designed to upgrade knowledge prior to reading one of the text versions. Results indicated that students who read the revised text recalled significantly more material and answered significantly more questions correctly than students who read the original text. Further, it appeared that the effects of background knowledge and more coherent text may be additive, that is, there may be separate effects of knowledge and coherent text. The results support the importance of the teacher's role in mediating learning from social studies text. (Four tables of data and two figures are included, and 29 references are attached.) (Author/MG)