The proportion of school leavers going on to "positive destinations" has fallen for the first time in five years, according to government figures.
Figures show 8.6% of pupils became unemployed after leaving school - up from 7.9% last year and the first time the figures have risen since 2011-12.
But the numbers from the poorest parts of Scotland leaving school with at least one Higher has increased.
The education secretary said there was "still more to do" to raise attainment.
Speaking as the figures were published, John Swinney said reforms announced last week were aimed at tackling the problem.
The Scottish government figures also show that the gap between school leavers in the richest and poorest parts of Scotland going on to positive destinations has grown.
The gap has dropped from 13.3 percentage points in 2011-12 to 10 percentage points in 2014-15, but rose to 11.2 points last year.
The Scottish Conservatives said the figures were another indicator on education which had gone down on First Minister Nicola Sturgeon's watch.
School leaver destinations
The Scottish government classes higher education, further education, training, employment, voluntary work or an activity agreement as "positive destinations".
The non-positive destinations are divided into "unemployed seeking work", "unemployed not seeking work" and "other".
The party's education spokeswoman, Liz Smith, said: "The number of young people going on to positive destinations is one of the first minister's go-to statistics when she is under pressure.
"Now she can't even say that is increasing. What's more, the likelihood of a school-leaver ending up at university, college, training or work is still far too dependent on their background.
"No real improvement has been made on that front either, and the SNP is running out of excuses about why that is."
Scottish Labour has also criticised the government over the figures, saying they were a "black mark" against the SNP's record on education.
Iain Gray, Scottish Labour's education spokesman, said: "Nicola Sturgeon promised to make education her top priority. Instead the gap between the richest and the poorest has grown as opportunities for school leavers are closed off.
"Young people, especially those from the poorest backgrounds, are being failed by an SNP government which has made a mess of education policy in Scotland.
"John Swinney took over an education brief with a stacked inbox - and he has done nothing to show he is capable of addressing the scale of the problems."
Other statistics from the report show that in the most deprived areas, 42.7% of those leaving school in 2015-16 had a minimum qualification of one Higher, up by 1.5 points from 41.2% the previous year.
However, in the most affluent parts of the country 81.2% of school leavers in 2015-16 had one Higher or more, a rise of 0.9 points from 2014-15.
Almost two-fifths (37.3%) of youngsters who finished school in 2015-16 went on to higher education, at either college or university, while 22.4% went on to further education college and more than a quarter (28.7%) found work.
Overall, the number of school leavers with at least one Higher increased to 61.7% - up from 60.2% in 2014-15 and compared with 55.7% in 2012-13.
Mr Swinney said: "It is encouraging to see the number of young people attaining qualifications at Higher level or above increasing - and I am particularly pleased to see a notable improvement in the proportion of young people who are looked-after and care-experienced gaining a qualification.
"While this is a step in the right direction, there is still more to do to close the gap between our most and least vulnerable children, and raise attainment for all.
"That is what the reforms I announced last week are designed to do.
"By giving more power to schools, including more direct control over budgets, we will empower schools to target resources where they are needed the most to improve the life chances of all of our children and young people."