Green’s Dictionary of Slang

(UK black/teen) a term meaning naturally, of course, there is no more to be said.

2004		Observer 22 Feb. 7: Wigger-speak. Standard – end of story.
2005		Observer Rev. 14 Aug. 7/2: Standard – naturally, of course, as in: ‘Did you pull her?’ ‘Standard.’.
2017		theculturetrip.com ‘Guide to London Slang 10 Jan. 🌐 Standard – another word for ‘of course.
2020		G. Krauze What They Was 202: That’s peak, I say [...] standard fam.