All the stories submitted to the BBC 500 Words competition are added to a database of children’s written language, and analysed by experts.
Oxford University Press, said the research was integral to understanding how children use language and reflect on the world around them.
Mentions of football fell for the first time in five years, researchers found, while mentions of rugby have increased by 50% since 2024.
Children were also likely to mention popular toys like Lego, TV shows such as The Traitors, and characters like Cinderella and Snow White.
Last week, Windsor Castle played host to the grand final of BBC 500 Words – with young writers from across the country attending the reception, hosted by Queen Camilla.
The event – which saw the six winning entries read out by celebrities including Jodie Whittaker, Bradley Walsh and Sara Cox – will be shown during a special episode of The One Show on Friday.