Institute of Education:

New research into the progress of 500 children published today shows that young children who were the poorest readers – and the very lowest-achieving in their class – can go on to outperform the national average within two years. They must be given four to five months of one-to-one tuition by specially trained Reading Recovery teachers for about 30 minutes a day while the children are aged six.
The research by the Institute of Education into the Every Child a Reader project shows that boys benefit to the same extent as girls and that one-to-one tuition helps to reduce the gender gap. The presence of Reading Recovery teachers also helps the other children in the school who do not attend the Reading Recovery lessons.
The two-year research project looked at the reading and writing progress of the lowest achieving children in 42 schools in ten inner London boroughs with the biggest social problems. The eight poorest readers in each class, then aged six, were selected. Eighty-seven of these children had the benefit of the Reading Recovery special tuition programme and their progress was compared to a group of children of similar ability and backgrounds, who did not receive the same tuition.
After one year children who had received the tuition had reading ages that matched their chronological age, and were 14 months ahead of the children in the comparison group.

Complete report here.
Much more on Reading Recovery here.