Of anyone with even a remote interest in psychology, educators would be the ones who Jean Piaget's work is most relevant to. Piaget was a Swiss psychologist who studied child development, particularly in relation to education.
Piaget's career motivation was threefold. He had a strong desire to examine the questions of epistemology: what is knowledge? What is man that he may have knowledge? Secondly, he was exposed to psychoanalysis when working with a pupil of Sigmund Freud. Finally, he became interested in child development when administering intelligence tests to children alongside Theophile Simon.
Piaget intertwined these interests and created his own field of study, called genetic epistemology. He studied the origins of knowledge in child development. Some of his better-known work explains the developmental stages of knowledge. The most important part of this theory says that children must understand logically prior concepts before they can learn newer, more complex concepts.
Of course, this is valuable information for teachers, who can use this and Piaget's other ideas to improve their teaching strategies and the intelligence of their students.