妹(いもうと) imoutoは wa学(がっ)校(こう) gakkouへ e行(い)く() iku年(ねん)齢(れい) nenreiになっていません ninatteimasen。 My sister isn't old enough to go to school yet. Literal Younger-sister [topic-は] school [to-へ] go age [goal-に] has-not-become. 年齢になる ('reach the age for') uses ~になる for reaching a state. ~ていません is polite negative of ている — 'has not yet become.' The whole pattern conveys 'hasn't reached school age.' familyschooleducation~になる (become)
妹(いもうと) imoutoは wa学(がっ)校(こう) gakkouへ e行(い)く() iku年(ねん)齢(れい) nenreiになっていません ninatteimasen。 My sister isn't old enough to go to school yet. Literal Younger-sister [topic-は] school [to-へ] go age [goal-に] has-not-become. 年齢になる ('reach the age for') uses ~になる for reaching a state. ~ていません is polite negative of ている — 'has not yet become.' The whole pattern conveys 'hasn't reached school age.' familyschooleducation~になる (become)