The Qualifications and Curriculum Authority is to try to establish why pupils' achievement appears to go into reverse when they first move to secondary school.
Officials already suspect it is the weakest pupils who suffer most once they leave primary school.
Last week, research conducted by the National Foundation for Educational Research and the QCA found that all 11-year olds' reading scores declined between May and September - even those who had attended Labour's summer literacy scheme.
Now the QCA has launched a consultation document aimed at speeding up the exchange of vital information between primary and secondary schools.
And in February it will start a special exercise to examine pupils' progress in literacy from the middle of one school year to the next - cutting out the complicating effect of the summer holidays.
A small-scale project has already suggested that it is the most vulnerable pupils who suffer most.
In theory, secondary teachers already have a battery of statistics about their new intake, including key stage 2 test results, along with age-related scores in reading, spelling and mental arithmetic.
But in practice, says the QCA, much of the information is transferred too late in too many different forms to help. As a result, secondary schools fall back on their own tests, or assume that every child is at, say, level 3.
"The use of assessment information on transfer remains very patchy," says the consultation document, which wants responses on: * the detail of assessment information; * the format in which it should be transferred; * the date by which it should be transferred.
It includes a model information form for schools to consider.
Tim Coulson, the QCA principal manager for school improvement and support, acknowledged that primary schools face difficulties. They might lack clerical support, and it was often far from clear which school various children would actually be attending.
The document has been sent to a national sample of schools and is also available on 0171 243 9422 from Terri Elford.
Peter Wilby, page 21