Exploring reading and mathematics growth through psychometric innovations applied to longitudinal data

Individual growth curves yield insights about growth that are not available from any other methodology; and developmental scales based on conjoint measurement models provide unique interpretive advantages for investigations of academic growth. The advantages are apparent when: (1) 15 consecutive statewide reading growth curves are annotated with historical policy actions; and (2) mathematics growth, mathematics achievement standards, and the difficulty of mathematical skills and concepts are conjointly quantified. Sequential examples demonstrate what can be gained when educational measurement scales are constructed to exhibit general objectivity (i.e. the absolute location of a person or an item on the scale is sample independent).