Timeline April 2007: SNP election manifesto promises to reduce classroom sizes in the first three years of primary school to a maximum of 18. Manifesto also pledges to maintain teaching numbers, despite falling school rolls, to help deliver the policy.

Timeline

• April 2007: SNP election manifesto promises to reduce classroom sizes in the first three years of primary school to a maximum of 18. Manifesto also pledges to maintain teaching numbers, despite falling school rolls, to help deliver the policy.

• May 2007: SNP wins election and forms minority Scottish Government.

• June 2007: New Education Secretary Fiona Hyslop announces "staged progress" towards class size targets. The cost is estimated at £35m in 2008-09, £70m the following year, and £105m in 2010-11. Some councils question affordability.

• August 2007: Ministers sign Concordat agreement with local authority umbrella group Cosla. Under the agreement, councils are charged with meeting the class size targets "as quickly as possible".

• April 2008: Inquiries by The Herald reveal nearly half of local authorities have still not decided how they are going to meet the targets. Glasgow begins rebellion, stating that it will not be pursuing them.

August 2008: Landmark placing request court case rules that the only class size target underpinned by law is 30. The ruling effectively means councils cannot set binding class sizes beneath this level.

• October 2008: Survey by The Herald reveals that more than a third of councils have reduced the number of primary school teachers.

• February 2009: Official figures show just 13% of pupils in the first three years of primary are in class sizes of 18. Scottish Conservatives say at the current rate it will take the SNP government 87 years to meet the target.

March 2009: The number of teachers in Scottish schools continues to fall, with public sector employment statistics showing a drop of nearly 1000 between 2007 and 2008.

• June 2009: Frustration over progress grows as the Educational Institute of Scotland teaching union backs proposals for industrial action to fight for smaller class sizes.

• June 2009: Confidential Cosla paper drawn up with the Scottish Government suggests councils can avoid reducing class sizes in some schools depending on local circumstances.