But Mal Peet, chairman of the judges, said that quality writing was key.
The author, who won the Carnegie Medal for his novel Tamar earlier this year, said he hoped that "all six writers will be recognised as, and feel themselves to be, winners".
Two first-time novelists are among those competing for the pound;2,500 prize which will be awarded by a panel including adult critics and keen readers in secondary schools.
A Swift Pure Cry, by Irish author Siobhan Dowd (David Fickling Books), is about a 15-year-old girl coping with pregnancy, an alcoholic father and a repressive home life.
In Ally Kennen's Beast (Marion Lloyd Books), a boy about to leave foster care illicitly tends a giant reptile while failing to escape his past.
Exchange, by Paul Magrs (Simon Schuster), sees the lives of a lonely teenage boy and his grandmother transformed by an unconventional bookshop.
Anthony McGowan's Henry Tumour (Doubleday) was described in a TES review (August 18) as "a deeply uncomfortable book (with) an integrity that is impossible to ignore". Suitable for 14-plus readers, the book is about Hector and his battle with the tumour invading his head.
The Foreshadowing, by Marcus Sedgwick, follows a nurse cursed with seeing the future into the horrors of the First World War (Orion Children's Books).
Finally, John Singleton's Angel Blood (Puffin) tracks four damaged children as they escape from a sinister institution.
The shortlist panel includes Louise Kanolik, librarian at Loxford school of science and technology in Redbridge, Essex, and Helen Comerford, a student at Wakeman school, Shrewsbury.
Three more young judges from secondary schools are being recruited to help choose the prizewinning novel by early November.