Less than 40 per cent of those leaving school in the poorest parts of Scotland achieved this, compared to just under 80 per cent in the most affluent places, new figures showed.
Teaching unions described the finding as a “huge challenge” and warned that such results would have a “negative impact” on the life chances of many young Scots.
Overall figures showed the number of leavers going into work, training or further education reached a record high, with 91.7 per cent of all pupils who left school in 2013/14 going to one of these “positive destinations”, while 8 per cent were unemployed at the end of March this year.
However, there was a stark gap in the attainment levels of pupils from the most deprived and wealthy parts of Scotland despite improvements among each group in the last year.
Almost three-fifths (58.8 per cent) of school leavers in 2013/14 had passed at least one Higher or Advanced Higher when they finished secondary school – up from 55.8 per cent the previous year.
A total of 39 per cent of school leavers in the most deprived areas of Scotland achieved this, compared to 34.9 per cent of 2012/13 leavers.
The proportion of youngsters in the most affluent communities passing at least one Higher also rose, going from 77.4 per cent to 79.7 per cent.
EIS teaching union general secretary Larry Flanagan warned that the “attainment gap” had not narrowed enough despite policies such as the extension of free school meals.
He said: “Poverty continues to have a negative impact on the education and life chances of too many young people across Scotland, and the attainment gap between Scotland’s most and least deprived pupils continues to be a huge challenge that society must tackle.”
Labour’s shadow education secretary Iain Gray, echoing the EIS concern, said: “The attainment gap still persists – these statistics show that the poorest 20 per cent are still half as likely as the wealthiest 20 per cent to leave school with one or more Higher.
“That isn’t nearly good enough, and again begs the question as to why Nicola Sturgeon, after eight years in power, is just realising now that this is a problem.”
Lib Dem education spokesman Liam McArthur also said that the “figures remind us of the task at hand in efforts to build a fairer society in Scotland”.
Scottish Conservative young people spokeswoman Liz Smith, said the “attainment gap remains far too wide” as she called for action to improve literacy and numeracy rates.
Education secretary Angela Constance said: “School leavers from disadvantaged areas are improving faster but there is still a gap between those from the most and least deprived areas, and I am determined to tackle this.”