elementary school student; primary school student
Refers to a child attending elementary school (grades 1–6 in Japan). Neutral, everyday term.
My child will become an elementary school student next year.
I often played in this park when I was an elementary school student.
Next year, my little brother will start elementary school.
This is a dictionary aimed at elementary school students.
When I was in elementary school, I often played in this park.
幼稚園児 refers to a preschool-age child (roughly 3–6), whereas 小学生 refers to an elementary school student (roughly 6–12), so learners should not use them interchangeably for age.