The purpose of this study was to determine whether differences existed in academic achievement, attitude toward school, and self-concept of seventh and eighth grade junior high school students in comparison to seventh and eighth grade middle school students who changed from a junior high school or an elementary school to a middle school in Jonesboro, Arkansas. A further concern of the study was to determine middle school principles of the Jonesboro Middle Schools.The subjects who furnished data for the study were 808 randomly selected seventh and eighth grade students. The students participated as control seventh and eighth grade junior high school students during the first year of the study (197576), or as experimental middle school seventh and eighth grade students during the second year of the study (1976-77). Five groups were formed for each grade. Two groups of each grade participated as the control groups, and the remaining three groups of each grade served as experimental groups.The Gordon How I See Myself Scale and the McElhinney Middle School Questionnaire Pupil Attitude Toward School scale were administered to accommodate a separate-sample-pretest-posttest control group design. Data from the Metropolitan Achievement Test and the SRA Achievement Test were used to fit a nonequivalent control group design. The data pertaining to self-concept and attitude toward school were analyzed by a multivariate analyses of variance technique. Achievement data were analyzed by multivariate analysis of covariance. On-site interviews were conducted to determine the Jonesboro-actual-middle school principles.Six null hypotheses were tested at the .05 level of statistical significance. Hypotheses one and two were stated to compare mean achievement scores of seventh and eighth grade Junior high school students to seventh and eighth grade middle school students. No statistically significant difference was found between the seventh grade junior high and middle school students. A statistically significant difference was found between the eighth grade junior high school and middle school students. The difference favored the junior high school students.Hypotheses three and four were stated to compare self-concept mean scores of seventh and eighth grade junior high school students to seventh and eighth grade middle school students. No statistically significant difference was found between mean scores of either grade.Hypotheses five and six were stated to compare mean scores on attitude toward school between seventh and eighth grade junior high and middle school students. No statistically significant difference was found between mean scores of either grade.The results of the interviews indicated elimination of "inappropriate" social and physical activities, more emphasis on intramural activities, and development of extensive exploratory programs as strengths of the Jonesboro Middle Schools. The lack of provision for continuous progress, team teaching, independent study, planned gradualism and use of multi media material appeared to be weaknesses.Conclusions drawn from the findings were:1. Students who experience a rigid academic schedule of a junior high school may tend to score significantly higher on achievement tests than students who attend less rigid middle schools.2. Students who have experienced the junior high school may tend to form some negative feelings toward school if placed in a middle school, but not to a statistically significant degree.3. The attitude and self-concept of seventh and eighth grade students appeared to be unaffected by the reduction of "inappropriate" social and physical activities.4. Little change in instructional procedures of classroom teachers appeared to be apparent.5. The major change seemed to be the addition of exploratory programs in middle schools.6. During the in-service program too much emphasis may have been placed on exemplary middle school programs at the expense of providing emphasis on the best middle school for Jonesboro.