Student mobility is the process of describing how children move from one school to another for reasons other than promotion. Highly mobile students are defined as students who move six or more times during their school career. Schools that experience the constant flow of students moving in and out struggle with delivering consistent and effective instruction for both the stable and the highly mobile student. The effects that highly mobile students have on academic achievement and accountability have failed to be addressed by education reform initiatives. The results of student mobility continue to go unnoticed and remain a serious problem that impacts all aspects of education reform, contributing to the gap in achievement between the advantaged and disadvantaged. This dissertation examined the effectiveness of the Assessment and Assimilation Program, which was designed to support highly mobile students entering Best Middle School. In the study, student data from Best's highly mobile students (transcripts, discipline reports, and attendance reports) were used to measure the relationship between academic achievement (improved grades), attendance (increased time in school), and discipline (decrease in negative referrals) after attending Assessment and Assimilation at Best Middle School.