Educational stages are subdivisions of formal learning, typically covering early childhood education, primary education, secondary education and tertiary education. The United Nations Educational, Scientific and Cultural Organization (UNESCO) recognizes nine levels of education in its International Standard Classification of Education (ISCED) system (from Level 0 (pre-primary education) through Level 8 (doctoral)). UNESCO's International Bureau of Education maintains a database of country-specific education systems and their stages. Some countries divide levels of study into grades or forms for school children in the same year.

Education during childhood and early adulthood is typically provided through either a two- or three-stage system of childhood school, followed by additional stages of higher education or vocational education for those who continue their formal education:

The following table introduces the main concepts, although terms and ages may vary in different places:

For additional ISCED stages of education, see ISCED.

Sudbury schools do not use formal grade levels or educational stages. Instead, students ages 4 through 18 are intermingled in a democratic educational system, relying on a series of certifications to use equipment that may require specialized knowledge or safety procedures. These certifications are not typically restricted by age, but rather by demonstrated ability.

In Australia, children undergo thirteen years of formal education (plus non-compulsory preschool or kindergarten), usually starting at age 4, 5 or 6, and finishing at age 17, 18 or 19. The years are numbered from "Kindergarten" to 12.

In the Australian Capital Territory (ACT), primary school is Kindergarten/years 1–6, high school is years 7–9, and college or Senior Secondary is years 10, 11 & 12 (see table below).

In the Northern Territory (NT), primary school is Transition/years 1–6, middle school is years 7–9, and high school or Senior Secondary is years 10–12 (see table below).