WCAG 2.2
lower secondary education level
the two or three year period of education that begins after completion of six years of school and ends nine years after the beginning of primary education (opens in a new tab)
Note: This definition is based on the International Standard Classification of Education [UNESCO (opens in a new tab)].
Source: WCAG 2.2 definition of “lower secondary education level” (opens in a new tab) (W3C)