About 145,000 pupils received results on Tuesday

Education Minister Peter Peacock said the results showed the general trend of steadily improving performance in most subjects at all levels was continuing.

The pass rate for Higher exams has increased slightly to 71.2%, and there were more A and B grades awarded.

However, the Scottish Conservatives called for an independent inquiry to ensure standards are being maintained.

Higher English was passed by 66.1% of entrants, up 2.1 percentage points. Higher maths was unchanged at 67.8%.

Have your say: Exam results Age gap as pupils sit exams early Text results service successful

The Scottish Qualifications Authority said the positive results showed youngsters were better prepared and studying at "suitable" levels.

The overall number of Standard Grade entries fell this year by more than 22,600.

But this was partly offset by a rise of more than 5,000 in the number of youngsters taking the less demanding "Access" or the more demanding "Intermediate" grades.

A total of 142,799 youngsters sat the national exams this year, up from 140,789 last year.

Even if the results that students receive are very different to what they were expecting, there is often a positive outcome to the situation Christina Allon Careers Scotland

More than 500 different papers were set and 9,000 markers were on hand to handle some three million exam scripts.

Mr Peacock said: "Our education system is respected internationally as being among the strongest but we have the ambition and investments to do even better in future.

"Today's results show the professionalism of our teachers, the hard work of pupils and the support of parents. Our education system is making steady progress, exactly what I want to see."

Anton Colella, chief executive of the Scottish Qualifications Authority, said the results showed steady improvement overall in "a stable and reliable education system".

Scotland's local authorities also praised the system, which has come in for criticism in the past.

Invariably, when there is an increase in the pass rate for any particular exam or subject, some will question whether exams are easier James Douglas Hamilton Scottish Conservatives

Pat Watters, president of local authority umbrella body Cosla, said: "We in local government are proud of our education system.

"It is the biggest service provided by councils and is a great example of what we can deliver.

"Results are not everything, but it is very pleasing to see so many young people doing so well and benefiting from a first class state education system."

However, James Douglas Hamilton, education spokesman for the Scottish Conservatives, said: "Invariably, when there is an increase in the pass rate for any particular exam or subject, some will question whether exams are easier, pupils are smarter or the schools are more rigorously selecting who is allowed to sit - or a combination of some or all of these factors.

"We need an independent appraisal of the exam system to ensure that standards are fully maintained and that results are a fair reflection of the abilities of students - our young people deserve no less."

A total of 411,144 Standard Grade papers were taken this year, down 5.2% on 2004.

Gaelic recorded a rare 100% pass rate by pupils

Officials said the drop could mainly be accounted for by a fall in the number of S4 students and by some schools moving to Access and Intermediate level for some subjects.

Pass rates at the Access level continued to increase, and there was a similar picture for Intermediates.

A total of 164,053 Highers papers were taken, a slight fall on 2004. Officials said this was largely accounted for by a drop in S5 students.

The pass rate was 71.2%, compared to 70.7% last year and 69.6% the year before.

Some minority Higher subjects with tiny numbers of entries showed wild fluctuations.

In building and architectural technology, which was taken by just 31 pupils, the pass rate was just 9.7% compared to 72.7% last year.

Helpline open

No-one passed Higher electronics or Higher sports organisation.

But two subjects had a 100% pass rate. They were Gaelic, which 102 people entered, and hospitality - reception and accommodation operations, for which there was just one entry.

For Advanced Highers, there were 17,141 papers taken and a pass rate of 74.5%, an increase of 0.9 points on last year.

Careers Scotland operates an exam results helpline for pupils receiving their results.

The message to pupils was not to panic and to remember that help was at hand, no matter what their grades were.

The freephone number 0808 100 8000 will put callers in touch with expert advisers who have the latest information on Ucas course vacancies at colleges and universities across the UK.