The initiative, the first such statewide effort, has attracted widespread attention, since California, together with Texas, dominates the nation’s textbook market.

Many superintendents are enthusiastic.

“In five years, I think the majority of students will be using digital textbooks,” said William M. Habermehl, superintendent of the 500,000-student Orange County schools. “They can be better than traditional textbooks.”

Schools that do not make the switch, Mr. Habermehl said, could lose their constituency.

“We’re still in a brick-and-mortar, 30-students-to-1-teacher paradigm,” Mr. Habermehl said, “but we need to get out of that framework to having 200 or 300 kids taking courses online, at night, 24/7, whenever they want.”

“I don’t believe that charters and vouchers are the threat to schools in Orange County,” he said. “What’s a threat is the digital world  that someone’s going to put together brilliant $200 courses in French, in geometry by the best teachers in the world.”

But the digital future is not quite on the horizon in most classrooms. For one thing, there is still a large digital divide. Not every student has access to a computer, a Kindle electronic reader device or a smartphone, and few districts are wealthy enough to provide them. So digital textbooks could widen the gap between rich and poor.

“A large portion of our kids don’t have computers at home, and it would be way too costly to print out the digital textbooks,” said Tim Ward, assistant superintendent for instruction in California’s 24,000-student Chaffey Joint Union High School District, where almost half the students are from low-income families.

Many educators expect that digital textbooks and online courses will start small, perhaps for those who want to study a subject they cannot fit into their school schedule or for those who need a few more credits to graduate.