Number + 年级
年级 (niánjí) means "grade" or "year level" in an educational context, referring to the stage of study a student is in. It follows a number or ordinal, as in 一年级 (first grade) or 三年级 (third grade). It is the standard term used across all levels of schooling in China.
我的女儿今年上三年级了。
Wǒ de nǚ'ér jīnnián shàng sān niánjí le.
My daughter is in third grade this year.
他是全年级成绩最好的学生。
Tā shì quán niánjí chéngjì zuì hǎo de xuéshēng.
He is the student with the best grades in the entire grade.
一年级的小朋友们正在学写汉字。
Yī niánjí de xiǎopéngyoumen zhèngzài xué xiě Hànzì.
The first graders are learning to write Chinese characters.