By Michael Rosenfield, WBZ-TV

SALEM, NH (CBS) – Kayla Butterworth was just 12 years old when she fell through a gap in the bleachers at Salem High School in New Hampshire.

The middle school student had just finished a track meet at the high school and was walking up the bleachers when she either tripped or slipped and went through a 15-inch gap, plummeting some 15 feet to the ground below.

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She broke several bones and was in a wheelchair for eight weeks.

“Your children are everything to you,” said Kayla’s father Christian Butterworth, who spoke only to WBZ-TV. “You feel for their pain which she went through a lot of.”

Kayla’s parents have now filed a lawsuit accusing the school district of negligence. Court documents state “The lack of any protective netting or screen to cover the openings posed a hazardous and dangerous condition…”

The incident happened three years ago but the family’s attorney, Jeanne Trott, told WBZ-TV the lawsuit had to wait until the extent of the injuries and healing process were known.

“I don’t think a lot of people recognize these dangers that can occur at these high, grandstand bleachers,” said Butterworth.

Today Kayla is 15 and a freshman at the high school.

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Her broken bones have healed but it is unclear what lingering effects both physical and emotional there may be in the future.

School District Superintendent Michael Delahanty said the lawsuit comes as a “surprise.”

Delahanty told WBZ-TV changes were made to the bleachers, including some cross braces that have been installed, but “netting is not a consideration”. He adds it is still possible for someone to fall through a gap.

The town of Salem is also named as a defendant, but the town manager says the town will seek to have itself removed from the lawsuit.

“We don’t believe we have any liability here,” said Town Manager Keith Hickey. “We don’t maintain school fields.”

The Butterworths hope the lawsuit sends a message to school districts that changes need to be made to bleachers.

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“I know there’s some safety issues there that I would really love to see occur so this does not happen to anyone else,” said Butterworth.