Words can hurt just as bad as a stick or stone, sometimes even worse.
Words can prick your soul like a needle and stay with you longer than a welt from a rock. Language has power and it has the potential of being lethal. Kids don't think about that when they're teasing someone in the classroom. There's always someone being picked on, for reasons ranging from the shape of their ears to their obesity. No one is perfect and kids don't let others forget that.