Student Mobility is increasing on Long Island, NY, the site of the present study related to the demographic changes of increasing immigration and poverty. Mobile students often struggle academically, and are at risk for school drop-out or failure. Mobility is sometimes combined with other risk factors such as gender, ethnicity, limited English, special education classifications, attendance issues, and socioeconomic status. The instability created by students changing schools impacts all involved in the transition including school administrators, teachers, and non-mobile students. This study focused on mobility at a Long Island public school district as experienced by secondary mathematics students and secondary teachers. The students were classified as either mobile (low or high) or non-mobile and have taken the Algebra I Common Core Regents exam. Using historical student data, this study explored the effects mobility has on mathematics achievement, and to what degree additional demographic factors contribute to the mobile students' achievement. The analyses found that non-mobile students out performed mobile students on the Algebra I Common Core Regents exam based on an ANOVA, (F(2, 313) = 25.198 p < 0.001) and that attendance, being African American, transferring from an international school, being an English Language Learner, receiving Special Education Services and grade level in which a student transferred into the district all were predictors of performance for mobile students on the exam, based on a multiple linear regression. To gage the impact mobility has on the classroom climate, a sample of teachers were surveyed. This survey revealed teachers perception of mobility and how it affects instruction. This study provides information about an at-risk group and how to better support them academically in our classrooms. [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.]