An estimated 25 percent are -- and the signs can be tricky for parents to detect. That's why the American Academy of Pediatrics has developed a new policy that recommends doctors discuss bullying during checkups. "A kid who is being picked on has often been told, 'Don't you dare tell anyone!' 

But when he's given permission to talk by a more neutral adult, he'll readily share his experiences," notes Robert Sege, M.D., chief of ambulatory pediatrics at Boston Medical Center. "And sometimes the symptoms of bullying appear to parents like something else. I see moms all the time who bring their child in because he's been doing poorly in school and can't seem to focus. They think it could be an attention disorder when the child is actually being picked on." More red flags:

Changes in behavior -- your kid becomes moody, withdrawn, spacey, jumpy, anxious

Physical ailments such as stomachaches and bad dreams, or unexplained bruises and torn clothes

An inexplicable drop in grades or a sudden reluctance to go to school 

Need help? Check out Stop Bullying Now -- it's a site designed to help both parents and kids cope with big, bad meanies.