This report first summarizes studies that have assessed the effects of LRE at the elementary level, the junior-high and middle-school level, the high-school level, and multiple-grade levels. This section is followed by an overview of research related to the implementation of LRE. The last section summarizes studies that have been conducted on LRE in non-school settings. The report concludes that whatever the research design and regardless of grade level, virtually all the research reported shows that LRE has had a positive impact on student knowledge. Those studies that investigated changes in attitudes and behavior also report positive changes in these two areas when experimental (LRE) students are compared to control groups of students not exposed to LRE. Although the research findings consistently favor LRE treatment groups compared with their control groups, skeptics often counter that the studies are flawed in one or more ways, that the research is old or dated, or there are too few studies in too few contexts to be persuasive. Although these concerns have merit, the critics of any body of research must bear in mind the observations of education researcher N. L. Gage (1978): "The invulnerable piece of research in any field of the behavioral sciences is non-existent.... Thus the path to increasing certainty becomes not the single excellent study that is nonetheless weak in one or more respects, but the convergence of findings for many studies that are also weak, but in many different ways." 84 references