As thousands of school districts across the country are thrown into disarray by school closures, some of the biggest names in the world of education technology are stepping up with no-cost lessons for teachers and students.

Mandatory school shutdowns that began in the Bay Area four weeks ago have prompted an unprecedented rise in demand for virtual learning services, as teachers scramble to adopt digital education platforms that can replace the traditional classroom. The disruptive changes brought on by the county's shelter in place order have also left parents in a lurch, many of whom have turned to online resources as they balance working from home and managing their child's daily activities.

In response, three major, Mountain View-based online education companies -- Study.com, Coursera and Khan Academy -- are shifting gears, announcing new resources and free services.

Earlier this month, Study.com announced that it is donating 100,000 free licenses for its online content to schools and K-12 school districts, valued at roughly $18 million. CEO and co-founder Adrian Ridner said the company has been inundated with calls from administrators, teachers and parents who are all trying to make the leap to distance learning under difficult circumstances.

"Some schools and districts had plans and preparedness around distance learning and remote learning, but many just found themselves really overwhelmed trying to go online," he said.

Since early March, Ridner said Study.com faced the twofold challenge of having all his employees working from home on top of handling more inquiries than ever before. Given the desperation they were hearing, Ridner said he and co-founder Ben Wilson felt it was important to start handing out free licenses.

"We realize that it wasn't going to solve all the issues, but it was going to take some of the pressure off," Ridner said.

Though recipients who've snagged the first two-thirds of the licenses range from coast to coast, several local school districts have taken up the offer. The Mountain View-Los Altos High School District has licenses available to all teachers who want to supplement their distance learning plans. Teachers can tap into the lessons with Google Classroom through the end of the school year.

The Study.com's roughly 79,000 lessons are accessible on laptops and mobile phones, and some teachers have incorporated them into daily lesson planning, Ridner said. A teacher might stream one of the instructional videos and pause it to have discussions with students over Zoom. Though Study.com is still processing all of the requests, about 40% of the donated licenses have gone to schools with enough low-income students to qualify for federal Title I funding.

Ridner said he has been steeped in online education for close to two decades, and that it's been interesting to see it suddenly, if only temporarily, become a cornerstone of education for millions of students. He said Study.com can leverage its expertise to make the transition easier.

"Overnight it became the top concern of every single person in the country who has kids, or students in their community," Ridner said. "We're happy to do what we can to help."

Coursera, which provides college-level courses to close to 50 million users worldwide, has also taken steps to open up its trove of online classes to students for free. The company's "Coursera for Campus" platform is available at no cost to all university and college students impacted by campus shutdowns due to the spread of coronavirus.

College students will be able to complete courses through September, with monthly extensions available for those who need it.

The scale of demand for the services has been massive. Coursera spokeswoman Kristen Zeck said the company has received 96,00 inquiries from across the globe, including students and staff from more than 6,500 colleges and universities. In the U.S., enrollment in online classes over the past 30 days is up 566% compared to the same period last year.

The outlier in the trio of online education providers is Khan Academy, a nonprofit that has always offered its course content for free, but has launched new resources for teachers and families trying to adjust to learning from home.

Among those resources are daily schedules for students across all grade levels, designed to help kids stay on task in a self-paced environment where direct instruction has been replaced with online videos and reading assignments. Teachers can choose to incorporate Khan Academy's lessons on a case-by-case basis, or school districts can choose a more formal partnership with the nonprofit.

In a March 18 video posted just days after Santa Clara County announced it was shutting down public schools, Khan Academy founder Sal Khan said that the nonprofit has completely shifted priorities in order to provide guidance and resources to schools, teachers and parents.

"It's our duty to step up in this crisis," Khan said. "We never could've foreseen this type of situation, but we want to be there to support you."

Khan Academy has also launched a donation drive to keep up with rising costs of providing extra support and handle the surge in demand. Khan said the nonprofit had already been operating at a small deficit before the global pandemic hit, and said philanthropic donations can help Khan Academy support people globally, as close to 1 billion kids worldwide are out of school due to the pandemic.