A system used to categorize education, where each category represents a certain degree of educational attainment and mastery of skill. In the United States education levels are as follows: Early childhood education, followed by primary school (elementary school), middle school, secondary school (high school), and then postsecondary (tertiary) education. Postsecondary education includes non-degree programs that lead to certificates and diplomas plus six degree levels: associate, bachelor, first professional, master, advanced intermediate, and research doctorate.