Customer needs are met by products and services. Customer needs and expectations change over time. All systems are subject to interaction and suboptimization. Schools are systems. All system have common characteristics.
Variation shows how the system changes over time.
Study of variation using tools separates special from common causes. Stable systems allow leaders to predict and plan for the future and to improve the system. The whole cycle must operate for learning to occur. It can be planned and lead. A theoretical foundation is key to effective change.