At least 100,000 children from schools around the country are signed up to sing "Tell Me Why" at 2.45pm on December 9.
The song, specially written for 10-year-old singer Declan Galbraith, will be released on the same day as the world record attempt.
There is still time for your school to take part in the UK-wide children's choir. To order an application form: Email: firstname.lastname@example.org Tel: 01634 729 832.
Children taking part in the record-breaking attempt will be asked to donate pound;1 to Sargent Cancer Care for Children, a national children's cancer charity that funds teams of care professionals and provides families with practical and financial support, together with short breaks during or after treatment.
For more information about Sargent: Tel: 020 7891 4567 Email:email@example.com