Suppliers like Foxconn are using teenage vocational students to staff their factories, as efforts to cut costs by moving to parts of China where they can pay lower wages has left them without enough workers. Student interns can be paid less than full-time workers, and employers are not required to pay health insurance or social security benefits for them. Students in vocational schools are frequently required to work internships as part of their education, and there are many concerns about the means school utilize to get their students onto the assembly lines.
See "Students by Millions Fill Labor Gap in China", The New York Times, January 6, 2013