In the 18 primaries targeted last session, up to 67 per cent of primary 2 pupils have a spelling age matching or exceeding their chronological age and up to 63 per cent of primary 3 pupils.
There is considerable unevenness from school to school, however. The numbers rated level A in reading by the end of primary 2 range from 7 to 53 per cent. Level B in reading at the end of primary 3 was achieved by between 20 and 76 per cent of pupils, and in writing by 10 to 89 per cent.
Schools also report other spin-offs from the project such as better concentration, improved access to the rest of the curriculum, less need for learning support and good parental involvement.
Schools say a key factor is the provision of additional classroom assistants and nursery nurses for early years classes. The Scottish Office has pledged to recruit up to 5,000 classroom assistants across the country over the next three years at a cost of #163;66 million.
The majority of West Lothian's primaries have opted to arrange classes in a literacy block, usually three to four times a week, using as many adults as are available. Children move around "skills stations", spending 15-20 minutes working on specific activities.
But there is some concern that older primary pupils and other areas of the curriculum could be losing out from the emphasis on early intervention.A report notes that 21 primary schools switched the emphasis of learning support teachers to concentrate on the first two years.
"The issue cited as causing most concern was the knock-on effect this could have on older pupils who would have less time with the learning support teacher as a result, although most schools acknowledged the long-term benefits of concentrating time on the early years," the report states.
Officials say "it is vital that schools redress the balance of the curriculum once children have acquired the basic skills of reading and writing. The experience of the majority of schools is that children actually access other areas of the curriculum more easily and readily because of their improved reading and writing competence."
Schools with infant pupils in the greatest need are given additional funding under the early intervention drive, which the Government has now expanded to a #163;60 million programme spread over five years.
The 18 West Lothian primaries singled out for special treatment in the first three years have now been joined by another two, resourced by #163;185,600 from the Scottish Office and #163;214,400 from West Lothian's own coffers.
The schools stress the importance of developing the programme beyond the infant stages to sustain early gains.
Staff training in early numeracy begins later this month.