the.com/old school tie

means A tie or affiliation marking someone as a graduate of a particular (usually elite) school, used to signal shared background and unlock informal networks of favor and trust.

from Literal origin: the actual striped neckties worn by old boys of British public schools (Eton, Harrow, and the like), each with its own distinctive pattern, which alumni wore as a badge of membership. By the early 20th century 'old school tie' had become a figure of speech in Britain for the whole system of loyalty, favoritism, and clubby trust that such shared schooling created — the idea that wearing the right stripes could get you a job, a introduction, or a pass that merit alone wouldn't.