“I would just keep it to myself and tell only people that were really, really close to me,” Cindy Nguyen said after class. “We want to have our personal, private space.”

That blurred line between public and private space is what Common Sense tries to address.

“That sense of invulnerability that high school students tend to have, thinking they can control everything, before the Internet there may have been some truth to that,” said Ted Brodheim, chief information officer for the New York City Department of Education. “I don’t think they fully grasp that when they make some of these decisions, it’s not something they can pull back from.”

Common Sense bases all its case studies on real life, and insists on the students’ participation. “If you just stand up and deliver a lecture on intellectual property, it has no meaning for the kids,” said Constance M. Yowell, director of education for the John D. and Catherine T. MacArthur Foundation, which has provided financing.

But some media experts say that in focusing on social issues, Common Sense misses some of the larger, structural problems facing children online.

“We can’t make the awareness of Web issues solely person- and relationship-centered,” said Joseph Turow, a professor at the Annenberg School for Communication at the University of Pennsylvania. Children should learn things like what a cookie or a Web virus is, and how corporations profit from tracking consumers online, he said.

In San Francisco, the Schools of the Sacred Heart, related boys’ and girls’ schools, met with parents earlier this year to discuss their Common Sense pilot program with Sister Anne Wachter, the head of the girls’ school.

“The messes they get into with friends, or jumping onto someone’s site and sending a message,” she said. “They don’t know, sometimes, how to manage the social, emotional stuff that comes up.”