The electronic textbooks, which include "Biology" and "Environmental Science" from Pearson and "Algebra 1" and "Chemistry" from McGraw-Hill, contain videos and other interactive elements.

But it's far from clear that even a company with Apple's clout will be able to reform the primary and high-school textbook market. The printed books are bought by schools, not students, and are reused year after year, which isn't possible with the electronic versions. New books are subject to lengthy state approval processes, making the speed and ease with which ebooks can be published less of an advantage.

Major textbook publishers have been making electronic versions of their products for years, but until recently, there hasn't been any hardware suitable to display them. PCs are too expensive and cumbersome to be good e-book machines for students. Dedicated e-book readers like the Kindle have small screens and can't display color. IPads and other tablet computers work well, but iPads cost at least $499. Apple didn't reveal any new program to defray the cost of getting the tablet computers into the hands of students.

All this means textbooks have lagged the general adoption of e-books, even when counting college-level works that students buy themselves. Forrester Research said e-books accounted for only 2.8 percent of the $8 billion U.S. textbook market in 2010.

The new textbooks are legible with a new version of the free iBooks application, which became available Thursday.

The textbooks will cost $15 or less, said Phil Schiller, Apple's head of marketing. He unveiled the books at an event at New York's Guggenheim Museum. Schools will be able to buy the books for its students and issue redemption codes to them, he said.

Albert Greco, a professor of marketing at Fordham University in New York and a former high-school principal, said schools would need to buy iPads for its students if it were to replace printed books.

It wouldn't work to let students who can afford to buy their own iPads use them in class with textbooks they buy themselves, alongside poorer students with printed books.

"The digital divide issue could be very embarrassing. Because if you don't have the iPad, you can't do the quiz, you don't get instant feedback ... that is an invitation for a lawsuit," Greco said. "I would be shocked if any principal or superintendent would let that system go forward."

Greco said hardback high-school textbooks cost an average of about $105, and a freshman might need five of them. However, they last for five years.

That means that even if an iPad were to last for five years in the hands of students, the e-books plus the iPad would cost more than the hardback textbooks.

At the private Xavier High School in New York, student Omar Soria welcomed the idea of getting rid of printed textbooks.

"They get pretty heavy, about maybe one pound per textbook. And depending on all the other books, which is binders and notebooks, it can get pretty heavy," he said.

Apple also released an app for iTunes U, which has been a channel for colleges to release video and audio from lectures, through iTunes. The app will open that channel to K-through-12 schools, and will let teachers present outlines, post notes and communicate with students in other ways.

Greco called the new app "a shot across the bow" of Blackboard Inc., a privately held company that provides similar electronic tools to teachers. It, too, has applications for cellphones and tablets.

Apple also revealed iBook Author, an application for Macs that lets people create electronic textbooks.

According to biographer Walter Isaacson, reforming the textbook market was a pet project of Apple co-founder Steve Jobs, even in the last year of his life. At a dinner in early 2011, Jobs told News Corp. chairman Rupert Murdoch that the paper textbooks could be made obsolete by the iPad. Jobs wanted to circumvent the state certification process for textbook sales by having Apple release textbooks for free on the tablet computer.

Jobs died in October after a long battle with cancer.