What does K 12 education mean?

K 12 education is to understand the internal logic of students' learning and push it down layer by layer, so that students' grades can be improved obviously. For example, the first level is pedagogy, that is, to choose a good teacher, and most people stay at this level. The second layer is literature, which is to find good teaching materials. The third level of linguistics is to pay attention to language logic in lectures, so that students can understand and adapt to this stage. The fourth layer is cognitive psychology, which means that the basic process of minors' thinking is to develop a special point, and the process of education should also follow this law.