Hedgehog theory, finished product theory, barrel theory. It is mentioned in the "three theories and three principles" of kindergarten management that the theories of kindergarten management include hedgehog theory, finished product theory and barrel theory. Kindergarten, formerly known as Kaner Garden, was introduced from Prussia hundreds of years ago. Formerly known as nursery garden and kindergarten. This is a preschool education school. According to the Regulations on Kindergarten Work, kindergartens are institutions that provide care and education for preschool children over 3 years old. Kindergarten-age children are generally 3 to 6 years old.