The Kinder eggs promotion has been branded "questionable playground marketing" by consumer and nutritional experts.
Italian firm Kinder's promotion is part of a pound;2 million TV campaign for Kinder Surprise eggs.
Steps appear in the adverts, and CDs, concert tickets and opportunities to meet the band can also be won with 100 special tickets in Kinder egg capsules.
Sue Dibbs, senior policy officer with the National Consumer Council said: "This seems to take aggressive marketing in the playground a step further.
"I wonder whether this kind of a scheme involving role models and a supposed benefit to the schools is fair on hard-pressed schools and parents - especially when it involves promoting a foodstuff that is of such questionable value."
Dr Michael Nelson, a senior lecturer in nutrition at Kings College, London, agreed: "This sounds very iffy to me, outrageous even. This is a very questionable marketing campaign."