Children whose parents frequently read with them in their first year of school are still showing the benefit when they are 15, says an international study.
An Organisation for Economic Co-operation and Development analysis examined the long-term impact of parental support on literacy.
Discounting social differences, the study found children with early support remained ahead in reading.
It found a strong link between teenage reading skills and early parental help.
The OECD analysis, based on teenagers in 14 developed countries, found that active parental involvement at the beginning of school was a significant trigger for developing children's reading skills that would carry through until they were teenagers.
On average, teenagers whose parents had helped with reading at the beginning of school were six months ahead in reading levels at the age of 15.
The report says that parents did not have to be particularly well-educated themselves for this impact to be achieved.
What was important was that parents read books regularly with their children - such as several times a week - and that they talked about what they were reading together.
This parental involvement overrode other social disadvantages and in some countries could represent more than a year's advantage in reading levels at the age of 15 compared with children whose parents rarely read books with them.
The study, which draws on data from the international Programme for International Student Assessment tests, also found a link between teenagers' reading skills and continued engagement with their parents.
Everyday family get-togethers, where parents and children talk, could influence school performance, says the research.
"Eating main meals together around the table and spending time just talking with one's children are also associated with significantly better student reading performance in school," says the OECD report.