Cheryl Forbes, 17, suffered cuts, bruises and a fractured collar bone in the accident and later underwent surgery leaving her with scarring.
Miss Forbes, who was a pupil at Mearns Academy, at Laurencekirk, in Aberdeenshire, at the time of the incident in October 2010, sued bus operator Bluebird Buses, of Perth.
In the action it was said that it was windy on the day and that a gust hit the bus on the B9120 Laurencekirk to St Cyrus road.
A civil jury at the Court of Session in Edinburgh ruled that the firm were liable in the action.
They awarded £20,000 to Miss Forbes, of St Cyrus, near Montrose, in Angus, for her pain, suffering and inconvenience.
But they also held that there was 10 per cent contributory negligence on her part for not wearing a seat belt at the time.
In a statement issued after the ruling, Miss Forbes's solicitors, Thompsons, said the firm had decided to use double decker buses despite warnings from parents about weather conditions on parts of the route.
Miss Forbes added: "It was the most terrifying thing I've ever experienced.
"When the bus landed on its side I was thrown down violently and the pain from my collar bone was excruciating.
"It took me a long time to get over what happened and I still can't travel by bus.
"I just can't understand why the company insisted on using a double decker bus."
Her lawyer, Syd Smith from Thompsons Solicitors, said: "It's only by sheer luck that this accident did not have a more tragic outcome."