But an investigation into the ludicrous ruling concluded it was a MYTH and that Blu-Tack on windows is not a hazard.
The strange case came to light in a Government report that examines over-zealous health & safety practices.
The Blu-Tack ruling was made by the private firm that runs the primary school in Perth and Kinross, Perthshire.
But it was debunked by the Government's Myth Busters Challenge Panel. The panel contacted Blu-Tack's maker Bostik which said it was safe – and even advertises its product's use on glass.
The Myth Busters ruled: "Whatever the reason for banning Blu-Tack, it is not on health and safety grounds. "The manufacturer's website makes clear that the product can be used on glass.
"We see no reason why the children's creative work should not be displayed for everyone to enjoy."
The Blu-Tack case is one of 28 rulings made in the Myth Busters' first two months.
One council was criticised for claiming that villagers wanting to hang flower baskets from lampposts must have every one checked by a structural engineer - costing £70 each.
And a parish council ordered a mum to take down a swing she put up for her kids at an allotment.
The panel was set up by Employment Minister Chris Grayling, who said: "I'm amazed by the amount of nonsense talked by health and safety jobsworths."
Leader of the 13-strong committee, Health and Safety Executive chair Judith Hackitt, said: "The amount of cases the panel has taken on clearly shows the extent to which health and safety is being misused as an excuse for banning almost anything."
What's the most ludicrous thing you've seen banned using health and safety excuses?