No, sadly not a wind up. I got a little excited about this yesterday and started a second thread in Chat (Yes, I know I need to get out more)
www.mumsnet.com/Talk/_chat/1716719-Have-you-heard-the-news-story-about-the-dangerous-flapjacks
The Health and Safety executive have commented (not on the thread)
www.hse.gov.uk/press/record/2013/sun250313.htm
A spokesman for HSE said: "We often come across half-baked decisions taken in the name of health and safety, but this one takes the biscuit. The real issue isn't what shape the flapjacks are, but the fact that pupils are throwing them at each other - and that's a matter of discipline, and has got nothing to do with health and safety as we know it. We're happy to make clear that flapjacks of all shapes and sizes continue to have our full backing.