Young people are sharing information and engaging in politics and policy discussions online like never before, according to a new study co-authored by an East Bay professor.

But a vast majority of them want help discerning Internet fact from fiction, the study shows — a problem that some local civics teachers find all too familiar.

“We make them into good fishermen, but they don’t know how to cook a fish,” said Gerson Castro, a history teacher at San Jose’s Gunderson High School and an advocate for mandatory civics classes. “They think they know, but they really don’t. I have kids who think Google is an encyclopedia.”

The study by the MacArthur Research Network on Youth and Participatory Politics found large numbers of young people across racial and ethnic groups are taking part in “participatory politics” — actions such as starting a political group online, circulating a blog about a political issue, or forwarding political videos to friends.

“At the easiest-to-implement level, something like tweeting about a societal issue would count as participatory politics,” said Joseph Kahne, a Mills College education professor who co-authored the study with the University of Chicago’s Cathy Cohen. “A large amount of the information that young people and probably all people get, they’re getting through social networks distributed by their family and friends.”

The national survey questioned 3,000 people ages 15 to 25 from February 2011 through July 2011 on how they use the Internet and social media and how they engage in politics. Unlike earlier studies, this one included large numbers of black, Latino and Asian-American respondents, allowing for unique statistical comparisons across race.

In generations past, a political party or campaign might’ve shaped and tightly controlled a message, while mass media editors and producers might have chosen to report what they deem most newsworthy. Now, youths are bypassing those elites and institutions, Kahne said.

“Young people themselves are getting to play that gatekeeper role and have an influence over what those in their networks pay attention to,” he said.

But sometimes they’re paying attention to information that isn’t true. Kahne said he was amazed that 84 percent of those surveyed believe they and their friends would benefit from learning more about how to tell if online information was trustworthy.

It’s a cry for help, he said.

“What’s heartening is that young people recognize it, but what we need is for educators to catch up and be providing those supports,” he said.

Castro said his students have access to more information than any other generation ever has, yet start out with little idea of how to assess and assimilate it.

He and other teachers are still trying to define their roles in helping students discern between truth, opinion and lies online when it comes to politics and policy. Some believe it’s the teacher’s job to help students filter the information torrent, while others think it’s more a parent’s purview.

Either way, those who have grown up in the cut-and-paste age of academic research need more guidance, he said. “Instantaneous information is not a bad thing, but how do we get them to want to dig deeper?”

Sam Weaver taught civics this past year at Pleasanton’s Amador Valley High School, which has fielded a nationally competitive civics team in 10 of the past 20 years. And as a student in that school’s Class of 2000, he was on the team.

“I always tell students you need to be aware of where you’re getting your information from rather than just accepting it as fact,” he said. “And I always try to challenge the students’ beliefs even if I agree with them 100 percent. … That’s part of the discovery process.”

Tweeting links and sharing videos on Facebook is a good start, he said, “but I still think we need to encourage people to go from that social media contribution to a more traditional participation” such as voting, writing to lawmakers, petitioning and taking part in political events.

That’s less of a hurdle when it’s an issue students care about personally, Weaver said: Proposition 8, the state constitutional amendment barring gay marriage approved by voters in 2008, galvanized many students to publicly oppose the measure, as have the Pleasanton school district’s budget woes, he said.

“It’s not until it hits home, sometimes, that it’s easy to get them involved,” Weaver said.

Josh Richman covers politics. Follow him at Twitter.com/josh_richman. Read the Political Blotter at IBAbuzz.com/politics.