The tight-knit groups of academic high-achievers who owe some or all of their accomplishments to illicit use of Adderall (Ritalin). Very common in prestigious universities.
"Know where I can get some oxy?"
"I'd recommend asking one of the ritalin mafia guys. They know the right doctors."
The time period before and during finals when everyone is frantically studying all that shit they didn't pay attention to in class, usually with the help of perscription ADHD medicine. During this time the black market value of such drugs increases as students discover how scarce the drugs have become, with everyone denying their own secret stash as they search for more.
"Yo you got any ritalin bro?"
"Naw, sorry, it's the ritalin rush, ya know"