A leading children’s advocacy group is challenging the educational technology software industry, an estimated $8 billion market, to develop national safeguards for the personal data collected about students from kindergarten through high school.

In a letter sent last week to 16 educational technology vendors — including Google Apps for Education, Samsung School, Scholastic and Pearson Schoolnet — Common Sense Media, an advocacy group in San Francisco that rates children’s videos and apps for age appropriateness, urged the industry to use student data only for educational purposes, and not for marketing products to children or their families.

“We believe in the power of education technology, used wisely, to transform learning,” said James P. Steyer, the chief executive of the group. “But students should not have to surrender their privacy at the schoolhouse door.”

Tim Drinan, a Google spokesman, said that advertising was turned off by default in Google Apps for Education products like document-sharing and e-mail, though the system does scan students’ e-mail in some of the ways it would if ads were turned on, to provide services like spam and virus protection. He declined to comment specifically on the group’s letter.