Campus violence has been rising in this largest city of China, with blackmail, battles over lovers and escalating quarrels as the major causes, according to statistics from a local youth hotline.
The issue of school violence hit the headlines again this week after a video posted online showed one girl at a Shanghai school striking another girl's face, punching her in the stomach and kicking her.
According to the Shanghai Youth Service Hotline, campus violence accounts for 14 percent of recent youth cases.
While the majority of victims are schoolboys between 13 and 17 years old, some are much younger.
Mrs Lu's son just entered primary school this year. On a recent day after school he was dragged by several young boys into an alley, where they took his money, transportation card and cell phone.
"My son has refused to go to school ever since. He says every time he gets near the gate a voice asks him not to go. He always knocks his head into the wall, saying his brain is in a mess," Lu said.
Another parent surnamed Chen called the center to complain that his son, a junior school student, received facial injuries from his classmate. He is not the only victim in the class.