Apple has confirmed a Financial Times report that high school students interning at Foxconn exceeded their legal hours while working on the iPhone X production line.

The report relates to 3,000 high school students who take part in a three-month long work experience program.

Six high school students told the Financial Times they routinely work 11-hour days assembling the iPhone X at a factory in Zhengzhou, China, which constitutes illegal overtime for student interns under Chinese law.

The six said they were among a group of 3,000 students from Zhengzhou Urban Rail Transit School sent in September to work at the local facility run by Taiwan-based Apple supplier Hon Hai Precision Industry, better known as Foxconn.

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“We are being forced by our school to work here,” said Yang, an 18-year-old student training to be a train attendant who declined to use her first name for fear of punishment.

It’s usual for Foxconn to take on temporary workers in peak iPhone season, including students, but the FT reports that more seasonal workers than usual were recruited as Foxconn tried to make up for lost time on iPhone X production.