And many have a "cynical" attitude towards saucy pop videos, claiming stars such as Britney Spears are making up for a lack of talent by shedding their clothes.
Research among nine to 12-year-olds found the media were as useful as mothers for finding out about sex and relationships.
TV, newspapers and magazines were thought to be far more helpful than fathers in exploring such issues. Only 34% thought dads were a useful source, while mums and the media were both ranked highly by 66%.
The report, commissioned by bodies such as the British Broadcasting Standards Commission, the Independent Television Commission and the BBC, looked at how children interpreted sex in the media. It found a majority of children (two-thirds) believed they had seen TV shows or videos with too much sexual content. Only 36% of those opted to stop watching.
The research showed children were "savvy and literate consumers" who were able to make judgments about sexual content
As part of the research the youngsters were shown a number of pop videos including Britney Spears' I'm A Slave 4 U, and the promo for Lady Marmalade by Christina Aguilera, Pink, Mya and Li'l Kim.
One 12-year-old boy said of the Britney video: "She's selling us her looks basically. I think she's not got anything in between her ears and her voice isn't really that good either."
Although most of the 120 youngsters who took part had TVs in their rooms (89%), nearly 70% said they watched in the main family room.
And 50% said they had discussed issues with their parents after seeing something on TV.
Leading soaps EastEnders and Coronation Street were mentioned by some as helping to clarify issues about relationships, rather than youth-orientated shows such as Hollyoaks.