What matters in developmental assessment?

Many feel the urge to calculate a score or figure for a child's development by submitting him to some objective test of readily scorable items, without regard to the child as a whole. I suggest that instead of merely determining a score for a child's development we should try to understand development, and particularly the purpose of developmental tests, their limitations and the reasons for those limitations. We should continue to learn about development by following up all those many children in which for a variety of reasons the assessment was unusual or difficult.