In some Dutch elementary schools, the average performance of students over several years is significantly below the level that could be expected of them. This phenomenon is known as underperformance. The most important identifiable weaknesses that go along with this phenomenon are that (a) learning material offered at school is insufficient to achieve core targets, (b) insufficient time is allowed for reaching the minimum objectives of the curriculum, (c) instructional quality is poor, (d) insight into students' performance levels is insufficient, (e) insufficient or inappropriate special measures are taken for struggling learners, and (f) the school is experiencing prolonged dysfunctional organization. In most schools with underperformance problems, these weaknesses do not appear singly, but in combination with other factors. In underperforming schools, one also finds more instability in the school's leadership team; high mobility and frequent fluctuations in enrolment and staffing; and high percentages of children at risk due to multiple risk factors, including student learning ability, poverty, ethnic minority status, first language, and other factors.