Simon Chittock, a sixth-former at Woodbridge school in Suffolk, was left disabled after falling on his back skiing during a school trip in Austria. The day before the accident Mr Chittock, now 23 but 17 at the time, had skied off-piste with another boy.
The boys were reprimanded and told not to do it again. Last year, the High Court found that the independent school was 50 per cent to blame for the accident because the school should have withdrawn the pupils' ski passes.
Mr Justice Leveson said that although the boys' behaviour showed "sheer stupidity", the school was in breach of its duty of care because staff failed to react appropriately to a demonstration of irresponsibility. But this week the Court of Appeal overturned the decision. It said that the teacher was "acting within a range of reasonable responses open to him".
Gary Hay, of Weightman Vizard solicitors which represented the school, said: "Schools have a duty of care but the ruling shows the courts should look for something extraordinary to find liability."