go to school学校へ means “to school,” and 行って is the て-form of 行く (“go”). It commonly combines with other words: 学校へ行っている means “attend/go to school,” while 学校へ行っても means “even if [someone] goes to school.”
JA: 毎朝、妹と学校へ行っている。
EN: I go to school with my younger sister every morning.