noun
alma mater; one's old school
Refers to the school (elementary through university) one previously attended or graduated from. Carries a sense of personal connection and is used in both formal and casual settings.
彼は母校の同窓会に出席した。
He attended his alma mater's alumni reunion.
母校の先生に久しぶりに会
I met a teacher from my old school for the first time in a while.