Okay, this tangent is so long I decided to give it it's own subpage.
I encountered the word sukeban in the book Womansword: What Japanese Words Say About Women, by Kittredge Cherry. (Tokyo; New York: Kodansha International, ©2002, first edition ©1987.) Keep in mind that since the book was originally published in 1987, the usage of this term might be outdated. Here is a section of Cherry's explanation of sukeban, from pages 51-52, reprinted here without permission.
Certain girls want to stand out in Japan. Whether these girls ride with motorcycle gangs or hang out in the urban jungle, their outlandish clothes and rainbow-streaked hair demand attention. English speakers might call them delinquents, but Japanese slang terms them "boss girls" (sukeban), a nasty contraction of suke, the word gangsters use for their female companions, and "gang leader" (bancho). These boss girls lead the increasing number of Japanese girls who are caught engaging in antisocial or criminal behavior.
Japanese can pick out a potential sukeban on the basis of defiant acts so subtle that Westerners would term them self-expression. For example, pamphlets printed by the Japanese police in the 1980s include sketches of girls in school uniforms demonstrating such "omens of downfall" as colored socks, rolled-up sleeves, permed hair, and lengthened skirts. In Japan's extremely homogeneous society, even these minor dress-code violations become significant. Schools, especially private ones, often have elaborate rules governing their students' appearance and behavior both in and out of school, and they send employees to coffee shops and movie theaters to check for violators. The sukeban use peer group pressure to enforce their equally strict nonconformist dress code of flamboyance.
Okay, no one could accuse any of the Azumanga Daioh girls of being delinquents, with the possible exception of Tomo. And actually, I don't think Tomo's bad
All this rampant innocence is precicely what makes the idea that "Chiyo-suke" could be derived from sukeban so funny.
I mean, think about it . . . colored socks. Hmm. Kagura's socks are purple. Tomo's are pink or salmon or something like that. Sakaki's are black. Yomi's are not only dark brown, they're also thigh-highs. Ooh, she's a bad'un. Only Chiyo and Osaka (and the "background girls" like Kaorin and Chihiro) wear normal white socks with their school uniforms.
Now think about Kaorin's dream sequence. She imagines that Yomi, Tomo, and Osaka are part of a scary (and kind of weird) street gang, with an evil looking Chiyo as their boss. (Actually, Chiyo looked pretty darn cool in that black coat and hat.) I don't know what the heck was up with Osaka's funky costume, but both Yomi and Tomo are depicted with ankle length skirts on their school uniforms. Note that bit in the sukeban explanation about lengthened skirts.
So . . . is there a dark side to Chiyo? Something the other girls, or at least Tomo and Kaorin, sense and subconsciously acknowledge? Maybe my depiction of punk-Chiyo isn't so far off.
Then again, maybe I'm full of crap.