Conducted from 1975 to 1977, this reading achievement study examined the effects of initial literacy in Navajo on later reading in English and the effects of initial arithmetic instruction in Navajo on later arithmetic instruction in English by comparing two groups of Navajo students, both of whom began school essentially monolingual in Navajo. The bilingual group consisted of students from Rock Point Community School who had first been taught to read in Navajo and then, at the second grade level, had also been taught to read in English. The second group consisted of students from a selected sample of BIA schools who had been taught to read in English only in English as a Foreign Lanugage (EFL) direct method programs. The study utilized existing programs in carefully selected schools. Students who had received bilingual instruction scored higher on standardized achievement tests than did students at comparable schools who had received English-language-only instruction and better than earlier Rock Point students who had received English-language-only instruction. Also, the bilingual students who were taught arithmetic in Navajo and English until the end of the second grade had significantly higher mean scores on the Total Arithmetic subtests than did the EFL direct method group at grades above the fourth. The major portion of the monograph consists of Appendix A, which describes other related studies and Appendix B, which details the Rock Point Study's methodology, findings of the study, and a statistical analysis. (CM)