Urban slang for a controlled substance regulated under the Controlled Substance Act. The substances are listed in a series of "schedules" numbered I through V, depending on when it was first subjected to federal regulation. These substances can be found at 21 C.F.R. § 1308 et seq.
"The five-oh came a'runnin' to pick up dem hoppers slangin' on the corners, but dey stopped me, and I had'a'had a little schedule in my pocket I forgot about."