Plans to reduce class sizes and expand provision of nursery education will be unveiled by the Scottish Executive next week.

Fiona Hyslop, Education Secretary, will use a Holyrood debate on Wednesday to set out her stall on limiting class sizes and widening the availablility of childcare services.

The debate over the importance of smaller class sizes has dominated Scottish education in recent years and was a key battleground in May's election.

According to research, smaller class sizes, although expensive, can raise school attainment, and work best where there is a significant reduction in numbers and for children in the early years.

The executive is facing pressure to slash class sizes from unions such as the Educa-tional Institute of Scotland (EIS), which has threatened strike action in pursuit of a 20-pupil maximum in all schools and subjects.

The SNP manifesto pledged to reduce class sizes in P1, P2 and P3 to 18 pupils or fewer, but it is thought Ms Hyslop will not pursue the government's objectives by setting precise targets to be achieved by particular dates. She said the announcement next week would be the beginning of "staged progress" in primary, while headteachers will have the power to decide on class sizes in later years.

One significant hurdle will be cost. Estimates during the election suggested reducing class sizes in P1 to P3 would cost £35m in 2008-09, rising to £70m the following year and £105m in 2010-11.

The SNP's election manifesto also promised to deliver a 50% increase in free nursery education for three and four-year-olds, which would amount to an extra 200 hours a year on top of the current 400 hours.

The long-term goal of the executive is to deliver universal integrated early education and care services, similar to the Scandinavian model, giving every family access to affordable, high-quality childcare and support from the end of maternity leave.

In the short term they have also pledged to look at providing support for the increasing number of grandparents providing childcare for grandchildren under three.

Crucially, the SNP's manifesto expressed concern over the removal of nursery teachers in some council areas, and Wednesday's announcement is expected to detail how the executive intends to deliver access to a fully qualified nursery teacher for every nursery age child, starting with children in deprived communities.

"Early intervention in particular will be one of the hallmarks of the SNP's approach to government," said Ms Hyslop. "Already we have had discussions with officials to see what we can do to drive forward some of the issues with nursery teachers. That is one of the areas where we hope to have a constructive dialogue."

The executive will also consider improvements to the support services for children who have additional support needs.

Another issue is the expansion of nurture groups, developed by Glasgow City Council to provide basic socialisation skills for children from chaotic backgrounds who come to primary with little understanding of basic skills such as sitting, listening and sharing.