In more extreme cases, only about 33 percent of the same students remain. These schools, Kerbow notes, are no longer the same organization. They may have the same physical build ing and same grade-level structure, but their most essential feature, the students, has almost completely changed. In these schools, at the beginning of each year and almost daily during the year, each classroom teacher bears almost all of the responsibility for incorporating new students into the school. The new arrivals are accompanied by little or no information about their past performance or current needs.
Teachers cope in various ways, but their instruction suffers.
High levels of student instability in classrooms, Kerbow notes, tends to increase review of materials, which slows down the curricular pace and decreases the opportunity to learn for all students, not only those who are changing schools. In fact, Kerbow finds that schools that have high student mobility, compared to more stable schools, slow their curricular pace progressively beginning from grade one. Thus students in highly mobile schools, even those students who have not them selves switched schools at any time, are getting instruction and content that is approximately a year behind that of students in more stable schools. In sum, a lot of student mobility was generated by dissatisfaction with their current school or the possibilities of greater satisfaction at another school. Even the students who cited the attractiveness of another school as their reason for leaving actually moved to a higher achieving school less than 50 percent of the time.