school-age children
Refers to children of the age at which they should attend school, typically used in educational or legal contexts.
In this area, the number of school-age children is decreasing year by year.
学齢 means 'school age' itself, while 学齢児童 specifically refers to the children of that age.
児童 is a broader term for 'children' (often elementary school age), whereas 学齢児童 emphasizes the school-age aspect.
Compound of 学齢 (school age) and 児童 (children).