Twenty-eight female guards were unfairly dismissed by a security company because the client‚ Metrora.
Children, some as young as 13, enter rehabilitation centres to beat their drug addiction.
But many fear returning to their communities at the end of the course.
"It becomes very hard for them to go back to their communities and start living a clean, drug-free life," South African National Council of Alcohol and Drug Abuse (Sanca) deputy director Maria Gumede, who also heads the Horizon alcohol and drug centres, said.
Gumede said the centre was now faced with great challenges because children were using nyaupe (a mixture of dagga and heroin) instead of plain dagga.
"Drug abuse among children has increased at an alarming rate," Gumede said. "While we have noted a decrease in dagga smoking, we have seen a massive increase in the use of nyaupe.
"Between 2000 and 2004, children were using dagga and mandrax. From 2006 they shifted the focus to nyaupe, which is quite a serious problem."
She said most of the children who went to the centre were not only addicted but were also psychotic.
"How do you rehabilitate someone in a psychotic state? Some children buy nyaupe thinking they are buying plain dagga. Nyaupe is highly addictive and extremely dangerous."
South African Medical Association (Sama)president Kgosi Letlape said: "Another problem in South Africa is the misuse of pharmaceutical preparations containing narcotic drugs and psychotropic substances that are sold by street vendors and healthcare providers without a prescription."
Meanwhile, Sama said it would give its full support to today's celebration of the International Day Against Drug Abuse and Illicit Drug Trafficking.