ADAM van Langenberg was horrified when he saw Australian sceptic Richard Saunders demonstrate how consumers were being scammed by Power Balance wristbands, which claimed to improve strength by working with wearers' ''natural energy field''.

Mr V, as he is known at McKinnon Secondary College, had seen his students wearing the hologram bracelets, which were worn by sportspeople including former AFL player Brendan Fevola.

Questioning minds: Paul Poulios, Kieran Murray, Emma Glickman, teacher Adam van Langenberg, Aya Tamir-Regev and Julia Behrens. Credit:Joe Armao

''I realised this is what my kids were wearing, and got really angry,'' Mr van Langenberg says.

The next day he interrupted his maths lessons to demonstrate how spruikers used old carnival tricks to con people into believing their arms were stronger when wearing the $35 wristbands.