Student school mobility is defined as a school change for reasons other than a regular grade promotion. School mobility has been shown to have academic and behavioral effects on students, especially in the short term. The problem addressed in this study was the short-term negative academic and behavioral outcomes for students experiencing school mobility in middle school compared to their non-mobile peers in a large suburban school district. The purpose of this quantitative causal comparative study was to examine the extent to which school mobility during sixth, seventh, and/or eighth grade affected or was associated with eighth-grade student academic and behavioral outcomes in mobile students compared to non-mobile students. Social capital theory served as the theoretical framework for this study. Participants included 6,042 students enrolled in the eighth grade during the 2018-2019 school year with 1,418 mobile students and 4,624 non-mobile students. To determine if school mobility had an effect on academic outcomes, the Maryland State PARCC eighth grade test scores and the ELA test scale scores for spring 2019 were gathered. Data were analyzed with SPSS software using the Mann-Whitney U test. To determine if school mobility was associated with behavioral outcomes, eighth grade discipline referral levels for the 2018-2019 school year were gathered. Data were analyzed with SPSS software using the chi-square test of independence. Data analysis indicated significant differences in ELA PARCC scores for mobiles vs. non-mobile students, U = 2,333,798, z = - 12.957, p < 0.05 and a statistically significant association between mobility status and referral level, X[superscript 2] (2, N = 6042) = 48.07, p < 0.05. These results have implications for school intervention policy and procedures that address school mobile students as national policy typically does not include mobile students in their policies targeting academic achievement and behavior. Future research recommendations include examining the timing of and reasons for the school change. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]