gold standard
noun [ S ] uk/ˈɡəʊld ˌstæn.dəd/ us/ˈɡoʊld ˌstæn.dɚd/
(FINANCIAL SYSTEM)
金本位（制）
a system of providing and controlling the exchange of money in a country, in which the value of money (compared to foreign money) is fixed against that of gold
(GOOD THING)
（在同类事物中的）标尺，表率
something that is very good and is used for measuring how good other similar things are
I think "Sesame Street" is still the gold standard for preschool television. 我觉得《芝麻街》仍然是衡量学龄前儿童电视节目质量的标尺。