More schools in Wales need to close or merge to keep pace with declining pupil numbers, according to the Assembly government.
The country will have 40,100 fewer pupils of compulsory school age by 201314 - the equivalent of 104 primaries and 23 secondaries.
But a TES Cymru survey of Wales's 22 local education authorities shows there are already thousands of empty desks, with surpluses exceeding a fifth of capacity in several areas. And while some authorities have mergers and closures under way, some authorities with the biggest problems have yet to make concrete proposals.
In Ceredigion, which has the second-highest proportion of surplus school places in Wales, three-quarters of primary schools have fewer than 100 pupils.
Estyn and the Wales Audit Office have concluded that Ceredigion's current pattern of small schools supporting Welsh-speaking rural communities is "extremely expensive and represents an inefficient and ineffective use of resources".
But the report acknowledges the political difficulties faced by councillors and officers in putting through changes.
Last year, Denbighshire was forced back to the drawing board after proposals affecting 14 schools were challenged by teachers and parents.
Supporters of small schools - seen as vulnerable because of their high running costs - will take some comfort from a new report which says their pupils do as well educationally as contemporaries in larger schools (see page 4).
But the report, from inspection agency Estyn, also highlights weaknesses in leadership of small schools, and the greater challenges teachers face trying to provide suitable learning activities for classes with a wide range of pupil ages.
TES Cymru's survey of Wales's 22 LEAs shows surplus places already exceed 43,300 in just 13 authority areas across Wales - with the pupil population expected to fall further over the next eight or so years.
A fifth or more of primary places are surplus to requirements in Merthyr Tydfil, Torfaen, Gwynedd and Wrexham, while Bridgend and Merthyr have a similar proportion of empty desks in their secondary schools.
While Carmarthenshire has gone for closures, mergers and some new "area"
schools, Anglesey may remove temporary classrooms and use surplus classrooms for early-years education and community use - although it has not ruled out closures.
Ceredigion, Gwynedd and Powys are among those who have yet to get down to specific details. Cardiff has delayed its reorganisation until after new guidance on calculating the physical capacity of schools is issued by the Assembly government. The Vale of Glamorgan is also waiting on the guidance before it reviews places.
But a Government spokeswoman said the new guidance should not change the overall picture of surplus places in local authorities.
She said: "The latest statistical publication confirms that pupil numbers in Wales are falling and are expected to continue to fall. An increasing number of LEAs have been acting to remove surplus places through reorganisations and closures in recent years, but (this) rate is not keeping pace with the fall in pupil numbers."