old school tie 
noun British
1A necktie with a characteristic pattern worn by the former pupils of a particular school, especially a public school.He was the epitome of the American idea of an Englishman, willingly posing for photographs hailing a taxi on Fifth Avenue with a rolled umbrella, dressed in waistcoat, old school tie and bowler hat....
- He doesn't wear an old school tie anymore and has stopped donning a dinner jacket and wandering down to the casino of an evening, with a sporty gel on his arm.
- This may be seen today in corporate uniforms (airlines, hotels), identification badges, shoulder-tabs, and arm-bands; regimental and old school ties are merely rose-tinted nostalgia for lost fraternalism.
1.1Used to refer to the group loyalty, social class, and traditional attitudes associated with people who attended public schools: appointments based on social class and the old school tie...
- I didn't grow up on the North Shore, I didn't attend a Private School with blokes called ‘Hamish, Stirling, Campbell or Fothrington’ and I don't hail from that ‘Ra-Ra’ background of old school ties and Bentley's.
- The result, he hopes, will be a giant set of databases that show the web of connections that often fuel politics and policymaking, such as old school ties, shared club memberships and campaign donations.
- So we have the ideologues in a Labour Government re-establishing a class structure in this country built around school - the old school tie network, which our generation thought we had managed to kill.