A 15-year-old at Ellsworth High School was charged with starting the fire with a lighter after allegedly saying, ``I wonder if this will burn,'' police Lt. Harold Page said.
Donald Awalt, 14, of Ellsworth, was airlifted to a Boston hospital with third-degree burns. He suffered burns to his back, legs and head, Page said. His condition was not immediately released.
``This is just a prank gone horrifically wrong,'' Page said.
The entire school - about 500 students, many in costume - was at the ``Spook Day'' assembly in the school gymnasium when the flames broke out at the top of the bleachers.
Some people initially thought it was a joke when they saw the flames. Then students bolted for the exits in a panic.
The victim ran down to the floor, where students and a school worker used a fire extinguisher and a coat to smother the flames.
The 15-year-old was charged with reckless conduct, aggravated assault and arson and taken to a youth detention center in Charleston, Page said. The boy was remorseful and said he never intended for anyone to be hurt, Page said.