Fifty Shades of Grey word-search given to American schoolchildren by mistake

The students in Monessen middle school, Pennsylvania, were aged between 11 and 13

Jamie Dornan as Christian and Dakota Johnson as Ana Steele in Fifty Shades of Grey

Parents in the US are turning 50 shades of red over a raunchy word search puzzle given to middle school students based on the erotic novel and movie.

The students in Monessen middle school, Pennsylvania, aged between 11 and 13 were given puzzles based on Fifty Shades of Grey, the bondage-themed book by EL James that has been adapted to film and opens in cinemas on Friday.

The puzzles contained terms including "spanking", "submissive", "leather cuffs" and "bondage". Some other words on the list were more explicit.

Officials in the school district said they could not say who handed out the puzzles or how many students received one because the incident only became apparent on Monday.

Parent James Carter complained about it at a school board meeting on Tuesday night along with other outraged parents and said he tried to question the school's principal and dean of students about the puzzle his son received, but they refused when he insisted on recording their conversation.

“I asked my son who passed it out, and he said the teacher passed it out,” Carter told Pittsburgh's Action News 4. “I don't think this is what they should be doing in the 8th grade level.'”

District Superintendent Leanne Spazak said the incident was under investigation.