Michael Morpurgo, author of The Butterfly Lion and The Wreck of the Zanzibar, and Martin Tibbetts, chair of the National Association for the Teaching of English (NATE), both spoke at this year's TES Write Away presentation at Shakespeare's Globe in London.
Mr Morpurgo said that children needed "dream-time" - time to look, learn and listen and not sit down and write quickly in a given space of time. "I couldn't, and I bet most of their teachers couldn't either."
Mr Tibbetts criticised the prescriptiveness of the literacy hour which left only 20 minutes for creative writing.
Ten thousand children, aged seven to 14, entered the third TES Write Away competition for autobiographical writing, jointly administered by NATE and sponsored by McDonald's Restaurants Ltd.
Each of the 20 finalists was presented with a cheque for pound;100 and each school represented received pound;400 towards a writer's residency.
All the finalists present, one of whom had come from Dubai and another from Tokyo, watched a performance of
Hamlet starring Mark Rylance.
The six winning entries, chosen by Mr Morurgo and the poet Grace Nichols from the 20 finalists, were published in TES Friday last week. All five junior finalists will be published in this month's TES Primary magazine.
Write Away 4 will be launched in September.
Junior finalists: Jessica Behan, Colman middle school, Norwich; Michael Tash, Salford Priors C of E primary school, Worcestershire.
Junior winners: Harriet Daly, Dubai English Speaking School; Adelia Myslov, Yehudi Menuhin school, Surrey; Laura Shepherd, Pool C of E primary school, Leeds.
Senior finalists: May Abdulla, Ffynone House school, Swansea; Lily Arnold, James Allen's girls' school, London; Anna Beach, Orwell high school, Felixstowe; Katie Boon, St Aidan's C of E high school, Harrogate; Jenny Butler, King Edward VI school, Bury St Edmunds; Kate Clark, King Edward's school, Bath; Nehal Depani, Beaconsfield high school; Marion Grossmann and Jenna Kim, International School of the Sacred Heart, Tokyo; Alex Osborne, Ringmer Community College, East Sussex; Ciara Preston, Bablake School, Coventry; Guy Walding, Idsall School, Shropshire.
Senior winners: Jennifer Bailey, Loughton middle school, Milton Keynes; Greg Henderson, Glasgow Academy; Nahid Samsani, Notting Hill and Ealing high.