noun
cram school teacher
Refers to a teacher at a 塾 (juku), a private after-school tutoring or exam-preparation academy. The term is neutral and widely understood.
彼は塾講師として数学を教えている。
He teaches mathematics as a cram school teacher.
塾講師のアルバイトを探しています。
I'm looking for a part-time job as a cram school teacher.
講師 is a general term for lecturer or instructor; 塾講師 specifies the setting as a cram school.
Compound of 塾 (juku, 'cram school') and 講師 (kōshi, 'lecturer/instructor'). The exact historical derivation is straightforward from the component meanings.