It has surely escaped no one who has sat or stood in a classroom: Many kids can’t sit still. Call it Attention-Deficit Hyperactivity Disorder (ADHD) or a problem invented by the pharmaceutical industry to shove pills down Johnny’s throat, as frustrated teachers have commented.

But who needs pills when a fidget spinner can do the trick? The latest rage is a strategically shaped little piece of plastic that fits neatly into a child’s hand and can be bandied back and forth during lessons, jealously guarded from the kid at the next desk.

The whirligigs on wheels, now a USD 500m (about EUR 448m) industry, are so popular that whole school classes in Germany recently were thrown into turmoil when customs officials confiscated a 35-tonne shipload from China, partly on grounds that the metal ball bearings contained toxic chemicals.

After it was announced the toys would be destroyed, an inventive moulder quickly seized the chance to prove that the plastics industry really does produce solutions, not just products. To head off pandemonium in the classroom, the company has begun offering a new type of fidget spinner with a ball bearing made “entirely of high-quality ABS – quantity discounts available."