In late October, a sixth grader was kidnapped and a ransom of half a million US dollars was paid. But the boy was killed and there's no word on if the kidnappers were arrested. There have been a few other kidnappings over the past few months, but the situation hasn't even come close to epidemic levels. However, the Public Security Bureau and parents are taking notice and trying to keep the children safe.
Unfortunately, the children of wealthy Shenzhen residents are easy targets. There are plenty of expensive private schools throughout the city and very little supervision between the school gates and home. It is generally the younger students whose parents or grandparents pick them up from school--this practice usually stops around fifth grade (the age of most of the kidnapping victims). These students are also at the age when they understand their parents' wealth and openly talk about it.
There's a great post over at China Hush with some translated reactions of the situation.