This sequential methodologic elaboration study investigated differences between the middle school and the junior high instructional strategies and the effects on adolescent attitude toward science in school and science achievement. Subjects of the quantitative phase were 570 seventh- and eighth-grade students in one school in an urban school district in the midwest United States during a transition year from junior high to middle school. Germann's Attitude toward Science in School Assessment and the school district's Benchmark Exams were employed to measure student pre- and posttest attitude and achievement. Variations within grade level, gender, race, general ability, and socioeconomic group were evaluated. Results of split plots revealed no significant differences in science attitude between the experimental middle school group and the junior high control group at this phase. However, there was significant improvement in attitude in both seventh-grade populations, but no change in attitude in either eighth-grade population. No significant differences in attitude were found between males and females, Caucasian students and students of color, or students of different ability or socioeconomic groups. Significant increases in science achievement were revealed in the seventh-grade junior high control group, the eighth-grade middle school, and the eighth-grade junior high, but not in the seventh-grade middle school. No significant differences in achievement were found between males and females. Caucasians scored significantly higher in achievement than students of color. Average and high ability students scored significantly higher pretest to posttest, but low ability students did not. High ability students scored significantly higher than both average and low ability groups. There was significant improvement in science achievement for students in the sufficient socioeconomic status group, but not in the low socioeconomic status group. These results were discussed with the five science teachers, the principal, and a university consultant in the setting, who were the informants of the qualitative elaboration phase of the study. Ethnographic methods uncovered themes explaining differences and similarities within the two instructional strategies. Teachers' feelings and stages of concern were identified. The results are discussed in terms of effectively implementing changes in instructional strategies and assessing science achievement of early adolescents.