Pupils who sat their Standard Grade exams a year early are this week celebrating vastly improved Higher results, according to official statistics.

The latest set of exam results shows that pupils at schools which pioneered so-called "early presentation" of Standard Grade have benefited from an extra year of preparation for their Highers.

Although only a small number of schools have adopted early presentation for entire year groups - and results are not available for all of them - figures from the Scottish Qualifications Authority (SQA) show that some have seen significant improvement at Higher level.

Since 2005, when the Scot-tish Executive relaxed the guidelines surrounding when candidates can sit exams, a number of local authorities have allowed pupils to sit Standard Grades in S3.

The aim was to provide greater challenge in the early years of secondary education after inspectors warned that pupils switched off in S1 and S2 because of a lack of motivation.

Another benefit was seen to be the fact that once Standard Grades were out of the way, pupils would have more time to study for Highers which would give them better results and increased options for a career or higher education.

However, critics argued that such initiatives can damage less able pupils if they are not ready for formal exams and Peter Peacock, the former education minister, warned last year that the executive move should not be seen as an invitation to put entire year groups through their exams early.

Dalziel High in Motherwell, which presented pupils who had sat Standard Grades in third year for Higher English and maths for the first time, achieved 155 passes at grade A-C this year compared to 110 last year.

Keith Grammar in Moray also recorded a significantly improved set of Highers results in 2007 with 23 pupils achieving three or more Highers compared to 14 in 2006 and 10 getting five or more Highers compared to six the previous year.

John Aitken, headteacher of Keith Grammar, believes this year's Higher results have vindicated the school's choice of putting pupils through Standard Grade in S3. "I am delighted with this first cohort. The results are at the top end of our spectrum and we are very happy," he said.

Jim Logue, convener of learning services with North Lanarkshire Council, hailed the achievement of pupils at Dalziel. "The results clearly show the difference that the additional year of study can make for Higher pupils and we also know that it doesn't have a negative impact on our Standard Grade results," he said.

Graham Donaldson, senior chief inspector of HM Inspectorate of Education, warned against putting all pupils through early exams.

"We must all continue to probe the educational validity and impact of early presentation of entire cohorts. That means looking at opportunity cost - what is being lost as well as what is being gained," he said.

However, Eric Wilkinson, professor of education at Glasgow University, believes the exercise is worthwhile.

"A very substantial number of young people taking Standard Grade at Keith Grammar after just three years of secondary did well," he said.