noun
fourth year of elementary school; fourth grader
Abbreviation of 小学校４年(生). Used in educational contexts to refer to the grade or the student.
うちの子は来年小４になります。
My child will be in fourth grade next year.
小４の算数は少し難しくなる。
Fourth-grade math gets a little harder.
小学校 is the full word for elementary school; 小４ specifically refers to the fourth year or a fourth-year student.
Abbreviation of 小学校４年(生) (elementary school fourth year/student).