Parents at one American school were shocked when they saw that a word search handed to children contained word like 'bondage' and 'submissive.' 

The 'Fifty Shades of Grey' themed exercise was given to a class of 13-year-olds at a school in Monessen, Pennsylvania during a lesson this week, and features words relating to bondage and sex toys.

The Huffington Post reports the school has declined to comment officially on the matter, and says they are currently investigating the incident as a 'personnel' matter.

In an email to a local news station, school board member Roberta Bergstedt explained that only five students had received it:

"It was a huge but unintentional error and collected from the five students involved as soon as it was realized.

"Unfortunately one copy was taken by a student who then posted it on social media."