Old School - [n] A group committed to traditional ideas or practices, a class of people favoring traditional ideas. 一群偏愛傳統想法的人
A diplomat of the old school.
Please see Wikipedia for other meaning of “old school”
Old school hip hop
Old school gambling
Old school wrestling.
In the usage of "old school hip hop", "old school gambling" and "old school wresting", "old school" is used to describe "hip hop", "gambling" and "wresting", meaning - old traditional way of gambling, wresting, etc.