Student performance on assessments can be measured in two very different ways, both of which are important. Achievement describes the absolute levels attained by students in their end-of-year tests. Growth, in contrast, describes the progress in test scores made over the school year. In the past, students and schools have been ranked solely according to achievement. The problem with this method is that achievement is highly linked to the socioeconomic status of a student's family. For example, according to Educational Testing Service, SAT scores rise with every $10,000 of family income. This should not be surprising since all the variables that contribute to high-test scores correlate strongly with family income: good jobs, years of schooling, positive attitudes about education, the capacity to expose one's children to books and travel, and the development of considerable social and intellectual capital that wealthy students bring with them when they enter school. In contrast, value-added assessment measures growth and answers the question: how much value did the school staff add to the students who live in its community? How, in effect, did they do with the hand society dealt them? If schools are to be judged fairly, it is important to understand this significant difference.