Nearly a third of children do not reach the required level for literacy by the end of primary school, figures show.
Details published by the Scottish Government show 70 per cent of P7 pupils achieved the expected curriculum standard in 2017/18, while 75 per cent met numeracy requirements.
But the figures fall to 59 per cent and 66 per cent respectively for those from the most deprived backgrounds.
The statistics show the attainment gap in literacy between those from the least and most deprived neighbourhoods grows during primary school.
According to the figures, the “performance gap” between pupils from the least and most deprived areas is 23 percentage points by P7.
While the Scottish Government highlighted figures showing the number of primary school teachers is at its highest level since 1980, Labour said that across all schools, there are now 3,130 fewer teachers than when the SNP came to power in 2007.
Scottish Conservative shadow education secretary Liz Smith said: “Notwithstanding a very welcome rise in teacher numbers, there remain some grim statistics which will make worrying reading for parents and teachers right across Scotland.
“The fact that one in three pupils is leaving primary school without reaching basic standards in literacy is the main worry.
“This report also reveals little progress on closing the stubborn attainment gap, and Scotland continuing to suffer from low teacher numbers.
“For an SNP government which claims education is a number one priority, this should make shameful reading.”
The Scottish Government said the pupil-teacher ratio was 13.6, the same as the previous year, while the average class size for pupils in primary was 23.5, also same as the year before.
The Lib Dems said the inability to tackle class sizes was “symbolic of the SNP’s education failure”,
Labour education spokesman Iain Gray said: “These figures expose the utter failure of the SNP government to tackle attainment. We know that the attainment gap develops in early years – but the fact that in some cases it widens in primary is inexcusable.
“SNP ministers claim that education is the top priority – these figures show that the poorest young people are being failed badly.”
Education Secretary John Swinney said: “The proportion of primary pupils assessed as achieving the expected levels of Curriculum for Excellence increased by up to four percentage points. The increasing performance gap throughout the primary stages is not new – but on almost every measure at every level, this data shows the attainment gap between the most and least deprived areas is now narrowing.”