Both parties agree performances must improve
Labour and the Scottish National Party have clashed over reducing class sizes to improve educational attainment.
Labour has pledged to cut sizes during the early years of secondary school, but the SNP does not believe this goes far enough.
The SNP said it would cut numbers in primary one, two and three to 18 or less within five years in an effort to drive up standards.
Education Minister Cathy Jamieson said standards were a concern and further improvements were required.
The biggest investment you can make is to start at the beginning
The SNP's Mike Russell said the Scottish Executive had failed to tackle poor literacy and numeracy levels.
Speaking on BBC Radio' s Good Morning Scotland programme, Ms Jamieson said she was confident performance levels would rise.
She said: "We've known for a number of years that there is a particular problem of a
dip in attainment there.
"I want to ensure that in terms of literacy and numeracy pupils get the best opportunities.
"That's why we will reduce class sizes in the first two years of secondary in maths and English to twenty, and that's a move that's widely supported."
Cathy Jamieson: "Widely supported"
However, Mr Russell said the problem required greater action and criticised the executive's policies.
He said: "The biggest investment you can make is to start at the beginning.
"To do it in S1 and S2 is not a bad idea, but it's a remedial measure to make up for the failures in primary school.
"We can actually do better than that by making sure those failures don't take place, and that's the investment we need to see Scottish education for the good of Scotland and its young people."
Valerie Wilson, director of Scottish Council for Research and Education, said children in small classes with one teacher performed more effectively than in larger groups.
She said: "Those who gain most are younger children and children from deprived areas and backgrounds."