 These lesson blocks are horizontally integrated at each grade level in that the topic of the block will be infused into many of the activities of the classroom and vertically integrated in that each subject will be revisited over the course of the education with increasing complexity as students develop their skills, reasoning capacities and individual sense of self.This has been described as a spiral curriculum.Many subjects and skills not considered core parts of mainstream schools, such as art, music, gardening, and mythology, are central to Waldorf education.