Children who read for fun are likely to do better in maths and English than youngsters who rarely pick up a book, research suggests.
It found that reading for pleasure is more important to a child's development than how educated their parents are.
The research also reveals that youngsters with older brothers and sisters are less likely to do well in tests in the basics.
The study, by researchers at the Institute of Education, University of London, looked at the reading habits of around 6,000 children in the 1970 British Cohort Study.
It analysed the links between how often children read and their test results in maths, vocabulary and spelling at the ages of five, 10 and 16.
The findings show that children who read often at the age of 10, and were reading books and newspapers more than once a week when they were 16, got higher results in the three tests at 16 than peers who read less.
There was a 14.4% advantage in vocabulary, a 9.9% advantage in maths and an 8.6% advantage in spelling, the study found, after parents' background and reading habits were taken into account.
It said: "The influence of reading for pleasure was greater than that for having a parent with a degree."
The total effect on children's progress of reading often, reading newspapers at age 16 and being a regular library user was four times greater than the advantage of having a university-educated parent, the study found.
It also looked at the impact on test scores of having brothers and sisters and found that those youngsters with older siblings were less likely to do well, particularly in vocabulary. This could be because children in larger families spend less time talking one-to-one with their parents and have less chance to develop their vocab skills, the researchers suggested. There was less effect if children had younger brothers and sisters, although they may score lower on vocabulary.