A study in five authorities led by Dick Johnstone of Stirling University, the country's foremost researcher in languages, concludes the method is firmly established after only three years. Children and teachers are enthusiastic and most parents are behind them.
Professor Johnstone, who carried out a major research study on French and German teaching in primaries five years ago, said that the Gaelic Learners in the Primary School (GLPS) initiative was more limited than immersion or partial immersion through Gaelic-medium education but was bringing the language back to communities where it once thrived.
He told a conference in Stirling last week: "This is not an 'either or'.
It's a 'both and' because GLPS sits alongside MLPS (modern languages in the primary school) and English. You have got at least a trilingual educational experience for those children concerned but probably more than a trilingual experience if you accept that Scots are Scottish English. It's not the same."
Groups of teachers in Argyll and Bute, East Ayrshire, North Lanarkshire, Stirling and Perth and Kinross volunteered to teach Gaelic for up to an hour a week after taking a 20-hour course, funded by the Scottish Executive.
Other authorities such as Highland and the Western Isles are also involved.
Professor Johnstone said that the initiative produced far fewer hours of Gaelic learning than Gaelic-medium education and was more akin to the teaching of French and German in primaries. "It is having a good measure of success so far," he said.
Some schools feared that it would detract from learning French or German and that it would increase pressures on the timetable. "Some headteachers were not quite on board and had some reservations because they were not sure children could cope with two new languages as well as English. There is an issue there," Professor Johnstone said.
But international studies consistently showed that the more languages learnt, the easier it is to take on another. There were also benefits in studying English.
Professor Johnstone said that the Gaelic venture was not in conflict with other language initiatives and pupils enjoyed both.
"Pupils receiving GLPS plus MLPS should expect a richer and more varied curriculum, an extension to their overall language learning experience, an increase in confidence and a greater awareness of other languages and cultures," Professor Johnstone maintains. "There should be a clear benefit in their acquisition of higher order mother tongue skills, and a deeper appreciation of how language works."
His report notes that the initiative is only one of a number of measures to promote Gaelic. "Although it cannot deliver the levels of proficiency which arise from Gaelic-medium primary education, it none the less has an important role to play in helping a relatively hidden language of Scotland to assume a higher public profile," he concludes.
"It may encourage pupils to stay with the language beyond primary school and it may help to bring the language back into families and local communities."
A key aim is to give pupils a taste in primary so that they can follow it up in learners' classes in secondary. Professor Johnstone, however, admits there are difficulties in secondaries and that continuity and progression can suffer.
"Secondary schools have to find some way of responding to the competence of pupils," he said.
Gaelic Learners in the Primary School: an evaluation report. By Richard Johnstone, Hannah Doughty and Robert McKinstry. Published by the Scottish Centre for Information on Language Teaching and Research at Stirling University.