Sharon Millward from Worsley, Manchester, suffered moderate to severe Post-Traumatic Stress Disorder as a result of the incident in April 2000.
Today Mr Justice Hughes ruled that Oxfordshire CC, which runs the Thornbury House Secure Unit in Kidlington where the incident occurred, were 75% responsible for what happened.
Although the exact amount of the award has yet to be calculated, lawyers say Mrs Millward will now be due around£250,000 in damages.
The judge said the unit's management had failed to notify Mrs Millward - who only taught there once a week - of her attacker's history of violence, especially towards women.
'If the risk the boy presented to staff, and female staff, had been identified and communicated as it should have been, I'm satisfied that the injury Mrs Millward suffered would not have occurred,' said the judge.
However he said Mrs Millward's demand that the boy - named only as S - 'shut up' shortly before the assault was 'wrongly confrontational and risky'. It was said with a 'measure of sarcasm', and led in part to the attack.
For that reason Mrs Millward was herself 25% responsible for the incident, the judge ruled.
As well as being struck by PTSD, Mrs Millward suffered bruising to her arms and groin following the attack, during which tiles were thrown at her and she was kicked.
The exact amount of her damages will not be known until later today as her legal team have yet to calculate what her loss of earnings as a result of the incident will be.
STRAND NEWS SERVICE