the old school tie
noun [ S ] uk/ˌəʊld skuːl ˈtaɪ/ us/ˌoʊld skuːl ˈtaɪ/
（贵族私立学校校友间的）相互扶持;老校友关系网
the way in which people who have been to the same expensive private school help each other to find good jobs
The old school tie still has enormous power in such companies. 在这样的公司里，老校友关系网仍然有很大的影响力。