noun
middle grades of primary school (third and fourth grades)
Used in Japanese elementary school contexts to refer to the third and fourth grade years, between 低学年 (lower grades) and 高学年 (upper grades).
中学年の子どもたちは、低学年より落ち着いてきた。
The middle-grade children have become calmer compared to the lower grades.
この本は中学年向けに書かれている。
This book is written for middle-grade elementary school students.