The purpose of the analyses presented in this report was to identify differential patterns of mathematics achievement which could be ascribed to different mathematics textbook series used by groups of students over a two year span covering grades 7 and 8. This report is one of two reports that examine textbook-related achievement patterns for the X-Population. The other report is NLSMA Report Number 10 which presents analyses for other textbook series and for different samples of the X-Population (i.e. in grades 4, 5, and 6). In this report comparisons are made for eight textbook groups at the end of grade 7, at the beginning of grade 8, and at the end of grade 8. Forty-one measures of mathematical achievement were used as dependent variables. Twenty-four of these variables measured significant variation among the textbook groups after adjustment for initial differences in ability and mathematics achievement. Results of the analyses support the conclusion that different patterns of mathematics achievement were associated with the use of different textbooks. The analyses also support a distinction between the behavioral levels of computation and comprehension as measured by a battery of tests designed by the experimenters. (Author/FL)