Education expands agency's competency to produce. The expansion of competency and/or product are continuous in education. Education produces and industries reproduce. This essay explains this concept putting them together as competency theory of education. Engagement is important to expand competency; competency is a function of interaction between input, skill, and environment. Information is input. A compatible way of using input is skill. Skills vary in their genres and are complementarity. Environment affects engagement. Every engagement gives products such as new-experience, intra/interpersonal understanding, skill, value, behavior, goods. These products become input for a new-environment to give products. The cycle is education.