The Scottish Qualifications Authority (SQA) said pass rates at Standard Grade, Higher and Advanced Higher all reached their best-ever levels.
While the results will lead to joy for many pupils, the rising pass rates have prompted fresh concern that qualifications are being "dumbed down".
Exam results for 2012, which will be received through the post by 158,908 candidates this morning, showed the pass rate for Higher has increased by 1.8 per-centage points since last year to nearly 77% – the sixth year in a row it has risen.
The pass rate for Advanced Higher has climbed to 80.1%, while the pass rate for Standard Grade now stands at 98.9%.
Liz Smith, Scottish Conservative education spokeswoman, congratulated pupils and teachers, but said future reform of the exam system should ensure "academic rigour".
She added: "I am very aware of the public suspicion that there has been some dumbing down in certain aspects of the exam system.
"Employers especially find it hard to understand how there can be a continuous rate of improvement every year in all the overall pass-rates, both north and south of the Border, when they are also finding there is a lack of knowledge and basic skills among new recruits."
The Scottish Government and teaching unions leapt to the defence of the school system.
Michael Russell, the Education Secretary, said: "I am delighted with these results and would like to extend my congratulations to our school pupils and their teachers on another year of high achievement.
"These results are a reflection of the hard work and dedication they have shown across a number of months and their success is hugely merited. To suggest otherwise would belittle the next generation of ambitious young Scots."
Dr Janet Brown, SQA's chief executive, said pass rate rise reflected the value placed on qualifications, particularly in a difficult economic climate.
A spokesman for the Educational Institute of Scotland said it was normal for exam results to fluctuate from year to year.
He added: "This year's results show Scotland's qualifications framework remains robust, and continues to support Scottish education and allow pupils to earn certificates that are valued by employers and further and higher education providers."
Ann Ballinger, general secretary of the Scottish Secondary Teachers Association, insisted recent increases reflected growing familiarity with the courses and exams by teachers. She said: "It takes some time to become familiar with the courses, which in some cases have changed quite considerably, and that is why you see exam results improve in this way."
Neil Findlay, Scottish Labour's learning and skills spokesman, added: "I'm delighted so many of our young people have again excelled themselves at exams at all levels and it is a testament to all the hard work by pupils, parents and teachers alike."
One pass rate to fall was for the Scottish Baccalaureate exams, where 79.1% passed compared to more than 80% last year. There was also little evidence that such exams were growing in popularity with just a small increase in uptake from 174 entries to 182.
A revision of science exams at Higher was also snubbed by many schools. The SQA revamped Highers in biology, chemistry, human biology and physics to reflect significant changes in the field of science.
However, schools still had the option of taking the traditional exams and 33,431 pupils took existing courses compared to the 810 who moved to the new qualifications.
This year also saw an increase in the number of candidates taking subjects in Gaelic, including Standard Grade history and geography and Higher maths.
In Glasgow, the proportion of pupils achieving five or more Highers rose from 6.5% last year to 7.5% while the number achieving three or more Highers increased from 16.3% to 17.9%.
Stephen Curran, the council's executive member for education, said: "We made a commitment to raise the attainment and aspirations of our young people and these results prove we are achieving this."
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