Schlagring literally translates to "strike ring" but refers to brass knuckles or a knuckle duster. It's a word that immediately conjures a strong, somewhat aggressive image.
In the context of this song, which is very much rooted in a 'ghetto' or street persona, the word reinforces the artist's tough image and rejection of conventional education or 'softness'. Kurdo raps, "Scheiß auf dein Abitur, ich ficke mit dem Schlagring" (Screw your high school diploma, I'll mess you up with brass knuckles), directly contrasting academic achievement with street credibility and physical force.
Kurdo's "Ich Bin Ghetto" is a super direct and aggressive track where he basically tells everyone else in German rap to step aside. He's all about his street credibility and isn't afraid to brag about it, contrasting himself with other rappers he sees as soft or fake. He makes it clear he's not interested in academic achievements or traditional success, saying things like "Scheiß auf dein Abitur, ich ficke mit dem Schlagring" [Fuck your high school diploma, I'll fuck with a knuckle duster].
He's constantly asserting his dominance, whether he's talking about how other rappers used to be gangsters but are now "Oberarzt" [chief physician] or how he's going to crash an "Abi-Ball" [graduation ball]. Kurdo's whole vibe is about being a "Verbrecher" [criminal] and not caring about the police or what anyone else thinks. He even jokes about how he was the first to skip school and wanted the school to burn, while other rappers just have "schwule Fans" [gay fans]. It's a pretty intense and provocative listen, full of bold statements about his identity and his place in the rap game.