Two teenagers were given electric shocks by staff at a special needs school on the orders of a crank caller, it has emerged.One of the vulnerable youngsters needed treatment for first-degree burns. Seven staff at the controversial centre have now been sacked. The victims were both vulnerableFor part of their ordeal, the teens - aged 16 and 19 - had their legs and arms bound. One received 77 shocks and the other 29.Staff at the Judge Rotenberg Education Centre, near Boston, had received a phone call ordering the punishment for the youngsters who, the caller falsely stated, had been misbehaving.A report released to authorities in Massachusetts said the caller was a former resident with detailed knowledge of the staff, residents, and layout of the home. No motive was given.Seven members of staff at the centre - which describes itself as a special needs residential school for people with behavioural problems - have since been fired.School spokesman Ernest Corrigan said: "It was a perfect storm of things that went wrong that night." The centre is believed to be the only school in the US that uses two-second skin-shock punishments to change destructive behaviour. It has survived two attempts by the state to close it over allegations that its unorthodox methods amount to abuse.