Garnet Bell, 46, aimed his home-made incinerator on the stunned pupils sitting their A-levels at Sullivan Upper Grammar School at Holywood, Co Down. Several were injured, three badly - including one pupil who suffered 30 per cent burns.
Last night a jury at Antrim Crown Court took one hour and 35 minutes to reach its verdict at the end of a seven-day trial.
Parents and some of his teenage victims smiled as Bell, an unemployed electronics electrician of east Belfast, was found guilty of three charges of attempted murder, three of causing grievous bodily harm and one of arson. He was cleared of one arson charge.
Bell, a Sussex University drop-out and part-time stunt driver, gave himself up to police in the Irish Republic 48 hours after the attack in June last year.
He told police that he held a 25-year grudge against the school, which he claimed had given him "inappropriate career guidance".
But he denied intending to kill any of the pupils with his improvised flame-thrower - two gallons of petrol and paraffin attached to a converted fire extinguisher which had been fitted with a special nozzle.
During the trial the court was told that 31 pupils were in the closing stages of their A-level French and Technology examinations when Bell burst into the assembly hall and indiscriminately sprayed them with flames.
He told the jury that he did not mean them any harm. He was suffering terrible stress and sleepless problems and at the time was taking tranquillisers every 24 hours which he claimed had a dulling effect on his perceptions.
He had also rowed with his brother, Leslie, over their mother's will and just after the flame-throwing attack set fire to his brother's home in the fishing port of Portavogie, Co Down.
Bell then vanished across the border into the Irish Republic before he eventually surrendered himself to police in Limerick. The court heard that Bell, who underwent psychiatric treatment at one stage, was a stunt driver with a fascination for fire and used to stage shows driving an old car through bales of burning hay.
He will be sentenced today.Reuse content