Struggling young readers make dramatic improvements when they are given tailored one-to-one coaching by expert teachers, research suggests.
Every Child a Reader targets help to struggling six-year-olds
A study of around 500 six-year-olds suggested those on the Reading Recovery scheme caught up with their peers in 20 weeks - four times faster than normal.
The government-backed scheme also saw improvements in writing and motivation, the Institute of Education study found.
About 6% of primary school leavers do not reach the expected reading levels.
Reading Recovery, which is part of the government's Every Child a Reader programme, works by giving the poorest readers individual support from specially trained teachers for 30 minutes a day over 12 to 20 weeks.
An evaluation of the £10 million project, which is funded by the government and several charitable trusts, also found that those who did not get the extra help fell further behind their peers.
Researchers at London's Institute of Education followed 234 of the lowest achieving children in 42 schools in London.
They compared the progress in reading of 87 children who were taught through the Reading Recovery programme with 147 children with similar reading difficulties who had not.
Although the two groups started at very similar levels, after four or five months of specialist tuition, the Reading Recovery group gained 20 months of reading ability.
But those without the specialist help improved by only seven months and had fallen further behind their peers.
Similar results were recorded amongst some 373 children getting help through Reading Recovery programmes in 61 schools in Birmingham, Bristol, Liverpool, Middlesbrough, Sheffield as well as London.
The children had moved from an average reading age of four years 10 months to a reading age of six years seven months.
And there was also evidence that benefits were seen across the school.
Leader of the research team, Dr Sue Burroughs-Lange, said the progress made by those on Reading Recovery programmes was "startling".
Jean Gross, Director of Every Child A Reader programme, said more than 75% of pupils who had been behind were now achieving average literacy levels or above thanks to the programme.
She said: "Our research shows that it is not the type of reading scheme that is important so much as teaching that is exactly matched to what each child knows and needs to know."
She added: "Many reading programmes are off-the-peg. This is completely pupil-centred. It is a very good example of personalised learning par excellence."
However, the high costs of the scheme at £2,500 per pupil - about the same amount primary schools have for one child's education a year - have made it unaffordable for schools without extra financial support.
Mrs Gross said: "The cost of doing it may be high but the cost of not doing it is also very high.
"The repercussions for truancy, exclusion and crime are very big. It's a case of spend now to save later."
Schools minister Lord Adonis said the results were "great news for children and parents".
He added: "They show that with the right teaching and support virtually every child can become a successful reader after starting primary school."