Rising school rolls in some parts of Scotland could be the latest headache for the SNP Government in its efforts to drive down class sizes in P1-3.
Colin MacLean, the Government's schools director, has acknowledged the existence of the problem, telling a conference in Edinburgh last week that "it's a challenge which we need to continue having conversations about with local authority colleagues".
In the absence of specific funding, ministers have been relying on councils maintaining teacher numbers at 53,000, despite falling rolls, as a way of making progress towards the limit of 18 pupils in infant classes. But that option is not open to councils where rolls are rising.
"Hot spots" include East and West Lothian, Edinburgh, East Renfrewshire, the Inverness area, and parts of Aberdeenshire, Stirling, Falkirk and Perth and Kinross - even although, apart from Falkirk, their overall numbers are predicted to fall in the 2006-10 period.
Aberdeenshire Council - where primary rolls are officially set to drop from 12,300 in 2006 to 11,460 in 2010 - is having to spend pound;130 million from its own capital resources over the next five years to cope with expanding numbers and improve its school estate. Seven of its 17 secondaries are more than 100 per cent full.
In addition, the council would have to spend pound;22 million in building and recurring revenue costs if it was to limit all its P1-3 classes to 18.
"This is placing us in acute difficulties," Bruce Robertson, Aberdeenshire's director of education, says. "We need to build new roofs over new heads, and this cannot be done as well as reducing class sizes.
"We have 23 per cent of our primary schools with class sizes of 18 or less, but we are not in a position to positively discriminate in favour of extending that to the other schools - even if we wanted to."
Mr Robertson says his and other councils are having to transfer money from revenue budgets to capital, while they await a government announcement on kick-starting the schools building programme.
Mr MacLean said local authorities were tackling the commitment to reduce class sizes in P1-3 "in a variety of ways", including providing extra teachers to schools in deprived areas and maintaining teacher numbers despite falling rolls.
The Government provided a one-off capital sum of pound;40 million for 2007-08 so schools could add to their accommodation. Mr MacLean said further help was available from the regular capital allocations, which have been increased, and from the funding planned for later years which has been brought forward to 2009-10 in response to the economic crisis.