lower grades of elementary school
Typically refers to first and second graders, sometimes including third grade. Used in school contexts to distinguish from 中学年 (middle grades) and 高学年 (upper grades).
For children in the lower grades, easy-to-understand explanations are necessary.
This event was planned for the lower grades.
This picture book is made for lower-grade elementary students.
Children in the lower grades still can't write characters very well.
Everyone, from the lower grades through the upper grades, took part in the sports day.