The results have so impressed the Scottish Executive, buffeted this week by bad news on pupils' progress in English language (page four), that ministers have decided to dispatch a research report on the subject to every primary school in Scotland.
A programme known as "synthetic phonics" used in Clackmannanshire primaries has shown that the benefits, revealed by The TES Scotland five years ago in the first study of a group of around 300 P1 pupils, last until P5. All of the authority's 19 primaries are now using the system.
Lesley Robertson, Clackmannanshire's quality improvement officer, said it was "absolutely delighted" that early gains had been sustained and increased. The achievements of boys were particularly notable, "and that's not because the girls were not doing well by any means".
A report by the researchers - Rhona Johnston of Hull University and Joyce Watson of St Andrews University, who devised the system - appears to have confirmed the superiority of synthetic phonics (which concentrates on familiarisation with the letters and how they blend into words) over the more traditional analytic phonics method (which focuses on the words).
The debate, which has raged among experts for many years, will be aired at a major "phonics summit" south of the border on March 17, convened by the Department for Education and Skills.
The Clackmannanshire study is now likely to be a major focus of that discussion. At the end of P2, children taught by the synthetic phonics method were reading and spelling on average 11 months ahead of their chronological age. By P5, the advantages had increased so that mastery of word reading was 26 months beyond what would have been expected at the age of nine - compared with a seven-month advantage in P1.
But the most dramatic breakthrough appears to have occurred for boys. There were no differences in P2. But by P3, boys were a significant eight months ahead of the girls in word reading and had a slight, but not statistically significant, advantage in spelling and reading comprehension.
In P4 and P5, the same boys were seven months ahead of the girls in word reading ability. This means that when the children were 9.7-years-old, the girls had a mean word reading age of 11.6 years and the boys of 12.2 years.
Spelling and reading comprehension were significantly above chronological age, but there was little difference between boys and girls.
The boys using synthetic phonics had a reading comprehension which was five months ahead of their chronological age by P3, but five months behind in the same year when taught by the analytic phonics method.
The authors observe: "The advantage for boys that emerged in P3 was entirely unexpected; keeping parity with the girls would in itself have been a very good outcome. This superiority has now been maintained over three successive years.
"The children are currently being followed through P6 and P7, so that we can determine whether boys keep their advantage to the end of their primary schooling. It is not clear whether all synthetic phonics programmes will be so effective for boys, but it is evident that the methods used in our study gave them long-lasting benefits."
Dr Johnston and Dr Watson comment: "In learning to sound and blend, children are given a procedure that they can apply for themselves whenever they meet an unfamiliar word - so they have a method for decoding unfamiliar words when they meet them in text."
Further confirmation of the power of synthetic phonics came when the researchers scrutinised the performance of low achievers, whose progress showed signs of tailing off. They were reintroduced to the synthetic phonics principles in P5 and one group of 12 pupils, who had only gained six months in reading competence in P4, raced a year ahead of their age.
Leader, page 26
TAPPING IT OUT
Pupils at St John's primary in Alloa are taught the sounds for letters, typically t, a and p. The class gives the sounds of the letters, t, a and p, and then blends the sounds together to pronounce tap, while the letters are pushed together.
The teacher might hold up a picture of a word. Children pick out letters for the sounds they hear and place them together on their own magnetic boards.