IS YOUR KID ON K?

It's 5:30 on a Sunday morning, but the 400-plus kids at the Fantasy Ranch dance club won't be making it to church. Instead, amid sweeping lights and the raw thumps of the aptly named song Insomnia, they sing the praises of the most recent drug to hit central Florida: Special K. "It's the bomb," gushes Tom, a sweaty 15-year-old with a struggling goatee. "It will make you like this," he says, rolling his eyes up as if staring at his brain. "It's dreamy. You see the lights, like, bend."

Tom's friend Sara quickly pulls a glass vial from her bra. After...