This paper provides evidence regarding the effects of schools, teachers and teaching processes on enhancing eighth grade mathematics achievement in Nigeria and Swaziland. A principal conclusion is that the achievement of students in both countries was significantly affected by the school/classroom in which they were enrolled, once effects of family characteristics were controlled. However, the specific school and classroom level variables accounting for these differences were not the same in both countries. Explanations for these between country differences could be both methodological or substantive. The study does, however, show that differences in achievement not attributable to student family background are largely due to differences in teaching quality (the teacher's use of time for lecturing, testing etc.). Teacher effectiveness depends upon finding the appropriate mix of alternative uses of instructional time. Since this seems to differ according to locale, more local research on teaching quality is needed.