If anyone wants to read more on this, Gerry Shih wrote a series of articles in Dec of last year on the presence of these camps and the backlash that sends some Uyghurs into extremist groups that commit acts of terrorism or seek asylum in ISIS-held territory.
Chinese mass-indoctrination camps evoke Cultural Revolution
China’s Uighurs grapple with pull of extremism
In western China, thought police instill fear
The detainees had to criticize and be criticized by their peers. One by one, they would also stand up before 60 classmates to present self-criticisms of their religious history. Very Cultural Revolution
A Turkey-based TV station run by Xinjiang exiles said almost 900,000 were detained, citing leaked government documents. 900,000 people in "re-education camps"