The article explains the relationship between formal education and cognitive development in chapter 6 of Vygostky’s Thought and Language, “The development of scientific concepts in childhood; the design of a working hypothesis”. Subsequently, it frames the proposal of Vygotsky in Annette Karmiloff-Smith’s theory of cognitive development. The thesis is that formal education is fundamental in the child’s mental development because it enables the child to become aware of spontaneous thinking, that is, to recognize spontaneous thinking as a particular instance of a more general and abstract thought, namely, the scientific thought. Finally, I set up objections to this thesis and suggest that Vygotsky’s position is not incompatible with current research on conceptual development, but complements it.