“What you’re seeing is an organization pushing an agenda to improve education through technology coinciding with the self-interests of companies providing funding to that organization,” said Joel R. Reidenberg, a professor at the Fordham University School of Law in Manhattan. “If you had municipal governments providing Wi-Fi in poor neighborhoods, you wouldn’t need to subsidize the private sector to do it.”

Mr. Steyer dismissed any suggestion of conflicts of interest. He said that Common Sense Media was transparent about its financial relationships and that it had no problem biting the hands that fed it.

“We exist for one purpose: to promote the best interest of kids,” Mr. Steyer said. “If you help us do that, we will enhance your brand for the good work you do for kids and families. If you do bad things, we will publicly criticize you and try to regulate you.”

It doesn’t hurt Mr. Steyer’s cause that his younger brother is Thomas F. Steyer, a hedge fund billionaire whose political action committee, NextGen Climate Action Committee, has been a major contributor to Democratic campaigns. For its new advocacy effort, Common Sense has secured more than $20 million in pledges from donors, among them Tom Steyer.

The Steyer brothers grew up on the Upper East Side of Manhattan and attended elite private schools. Their father was an antitrust lawyer on Wall Street.

Mr. Steyer traces his interest in children’s education, and his gregariousness, to his mother, who was a schoolteacher in Harlem and the South Bronx. After he graduated early from Phillips Exeter Academy, he volunteered to work with his mother as a teacher at a high school for disadvantaged students in the Hell’s Kitchen neighborhood of Manhattan.

Mr. Steyer later became a civil rights lawyer, but he never stopped teaching. For the last 28 years, he has taught popular courses at Stanford University on civil rights, civil liberties and education. His students have included Cory Booker, now a senator from New Jersey, and Chelsea Clinton.