More than one in 10 teenagers frequently use the internet to look at "adult-only" websites, a government- backed study says.
Almost a fifth of pupils visited current affairs sites
Some 12% of 13 to 18-year-olds asked by the National Foundation for Educational Research said this was one of their main reasons for going online.
However, homework was the most common reason for internet use, with just over three-quarters citing it.
The findings are part of an eight-year study of 6,400 pupils in England.
The NFER, carrying out research on behalf of the Department for Education and Skills, found 52% used the internet for instant messaging services and 36% to shop for goods or services.
Some 18% looked up news and current affairs sites and 9% visited discussion forums.
The study looks at the effect of citizenship lessons - introduced across England in 2002 - on children's development.
It runs until 2009 and is based upon a sample of 237 schools and 50 colleges.
Among the students, television was seen as the most trustworthy form of mass communication, with 48% trusting it completely or a lot.
Older students were less convinced than younger ones of the level of honesty in the media.
Newspapers fared worst overall, trusted by just 13%.
The study found that citizenship lessons provided "a positive climate with students feeling free to express opinions and to bring up issues for discussion".
But opportunities to look at politics and the economy "may be limited by the existing curriculum and staff expertise".
Meanwhile, students' involvement in running schools was "limited", the report said.
It found 67% of students said they were "not very interested in politics".
An Electoral Reform Society spokesman said: "Voting and elections should be a compulsory part of the curriculum.
"Whether students then go on to take part is entirely up to them but they should be taught about it."
The report is called Listening to Young People: Citizenship Education in England.