It’s hard enough for adults to navigate the internet’s maze of content—editorial, “advertorial,” sponsored, or native. So it’s perhaps unsurprising that children have an even harder time telling the difference between journalism and advertising.

A study conducted by researchers from the departments of education and psychology at the University of Jyväskylä in Finland has found (link in Swedish) alarmingly low levels of web literacy among a sample of 160 sixth-graders.

Students read and evaluated a press release from a company that produces energy drinks. The text commented on the health effects of the drink, mostly the positive ones. The students’ task was to explore the health effects of the drinks. The results are not encouraging.

Only 21% recognised the site as unrealiable because of a commercial bias. Fully 48% of the students thought the site was a reliable source for investigating health effects of energy drinks. The remainder were equally divided between those who identified the site as unreliable but couldn’t figure out why, and those who identified it as unreliable but had a reason other than commercial bias.

“The Internet is an important learning environment for adolescents in schools and in their leisure time,” Carita Kiili, one of the researchers involved, wrote in an email to Quartz. “In order to take full advantage [of] online information, students need to be digitally literate.” Critical evaluation is a difficult task for sixth-graders, though an increasingly important one as social networks and online publishers inject subtle advertising into their content.

The study was part of the eSeek project, funded by the Academy of Finland, whose goal is to better understand the the new type of media literacy demanded by the web: ”Internet users must be able to search for information, evaluate information critically, take advantage of multiple sources and share what they have learned to others.”