The British Association for Modern Mosaic (BAMM) is running a mosaic competition which is open to primary school aged children.
   
The
competition is called MEGA MOSAIC MAKERS 2008 and it is
nationwide. They are aiming to raise the profile of mosaic art in
schools, with the principle of getting children interested at a young
age. It is  open to groups/organisations/workshops who work with
children under the age of eleven. Both teachers and students are
awarded prizes, which have been provided by the sponsor, Topps Tiles.
There is a group and an individual category. 

This year’s entry is open from now until 7th Nov 2008, and work can have been completed anytime in the last three years.

Link: http://www.bamm.org.uk/portal/content.asp?ContentId=1103