The Los Angeles Unified School District is demanding that Apple Inc. refund millions of dollars for Pearson software that had been loaded onto iPads for the district's 650,000 students.

If an agreement on the dispute cannot be reached, the nation's second-largest school district could take Apple to court.

Two years after the district launched the most expansive school technology initiative in the country, its attorney said it is "extremely dissatisfied" with the work of Pearson, the publisher of the Common Core learning software.

"While Apple and Pearson promised a state-of-the-art technological solution for [the technology program] implementation, they have yet to deliver it," wrote David Holmquist, Los Angeles Unified general counsel, in an April 13 letter to Apple.

Thousands of Los Angeles school students have struggled to access the Pearson lessons, sacrificing hours of learning time and adding to the issues arising from the district's controversial $1.3 billion technology partnership with Apple and Pearson.

The district hasn't disclosed how much of the $1.3 billion project it wants refunded, but documents obtained by member station KPCC show it has spent $3.3 million on Pearson's software so far.

The iPad program, meant to provide a tablet to every student, has a troubled past. Not only have students struggled to use the Pearson software but others have managed to bypass security to reach blocked websites.

In December, the FBI launched an investigation into LAUSD's iPad purchase, carting out 20 boxes of documents from the district office. No one has been publicly charged in the case.

KPCC reported last August that former Superintendent John Deasy and top district staffers had close ties with Pearson executives and communicated about details of the iPad project before the contract was awarded.

Pearson and Apple representatives could not be reached for comment Wednesday, but, when questions arose last year about its software, Pearson said it had fulfilled its part of the deal.

"The course content has been complete for over a year," wrote then-Pearson spokesman Brandon Pinette in an email to KPCC in September. "Yes, there are important enhancements to add as there always will be. We will add twice a year. No digital product should ever be considered complete."

District officials purchased the Pearson software even though it was unfinished. Teachers complained the material seemed rushed: Lessons were missing math problems and reading material and contained errors. The software also lacked many interactive elements that had been promised, teachers said.

"[Pearson] missed the whole point of technology — individualized instruction, all the material in the palm of your hand," said Ben Way, a math teacher at Alliance Tech Academy, a Los Angeles charter school group that also purchased Pearson's iPad software.

Los Angeles Unified Board Member Monica Ratliff said that when Pearson software issues went unresolved, students turned to other resources.

"Because Pearson just wasn't working out for them," Ratliff told KPCC. "We paid a lot of money for that curriculum, and we want our students to be able to use it. I think it's imperative that Pearson step up and fix the curriculum, or give us back our money so we can buy curriculum that does work."

Copyright 2016 Southern California Public Radio. To see more, visit Southern California Public Radio.