Parents who don't know about the net could be harming their kids' chances of getting a good job, researchers say.
Their survey found that 18% of mums and dads did not know how to help their children use the web safely.
Kids are much more switched on, with 98% of them saying they had net access at home, at school or somewhere else.
Researchers said: "Now that many young people rely on the net for information, the more it matters that some of them are getting left behind."
They added: "Not knowing how to best use the internet may have a negative impact on their education and employment opportunities."
The survey also showed that parents were really worried about kids being able to see bad things on the net, with 85% of them calling for tougher laws.
Around 1,500 nine to 19-year-olds and 906 of their parents were quizzed in the study by the London School Of Economics.