Teachers use the software to track students’ work and may intervene when a child is struggling. One-on-one mentoring helps students make choices and evaluate their progress. In a Facebook post in 2015, Mr. Zuckerberg said that this learning approach “frees up time for teachers to do what they do best — mentor students.”

Not all educators agree. Four former Summit teachers said they found the system problematic. They asked that their names be withheld, saying they feared repercussions for their careers.

At Summit, they said, they were required to teach students cognitive skills (like how to construct an argument) while making students responsible for teaching themselves underlying lesson material (like how diverse plants and animals coexist). But some students raced through lessons without actually understanding basic facts, the teachers said, making it difficult to help them structure arguments on specific topics, like climate change.

Ms. Tavenner of Summit, however, said that was exactly the point: to make students discover for themselves that they cannot succeed on applied projects without learning the fundamentals.

Students think to themselves, “‘Oh, I’ve got to actually go back and deeply understand it,’” Ms. Tavenner said. “Those are the habits of success that we are trying to instill in kids that simply don’t get instilled in the normal system.”

It can be a steep learning curve.

In 2015, Urban Promise Academy, a public middle school in Oakland, Calif., introduced the platform for its sixth graders. But students, accustomed to having a teacher’s guidance, did not know how to pace themselves, said Claire Fisher, the school’s principal.

“Kids were self-pacing to failure,” Ms. Fisher said.

Teachers remedied that by helping students set realistic goals. The school is now happy with the program, she said, and has expanded it to the seventh grade. Even so, Ms. Fisher said, “We definitely have a concern about the quality of the assessments in the curriculum and whether it actually promotes deeper learning.”