A plan to build housing in Palo Alto for regional teachers and school staff has received a major boost: a $25 million donation from social media giant Facebook.

Menlo Park-based Facebook and Santa Clara County Supervisor and Board President Joe Simitian, who has spearheaded the project, announced the donation Thursday morning. Simitian called it an "exceptional gift" for the future development at 231 Grant Ave.

"It helps our teachers. It helps our schools. And it helps our communities," Simitian said. "From the beginning, Facebook 'got it'...the importance of affordable teacher housing in the communities where teachers teach."

The money will increase the number of homes the project can offer — between 90 and 120 homes, up from a previous minimum of 60 units — and include staff from two additional school districts, East Palo Alto and Menlo Park. The housing will be available to teachers and school staff from the Palo Alto Unified School District, Mountain View Whisman School District, Mountain View-Los Altos High School District, Los Altos School District and Foothill-De Anza Community College District. Leadership from these districts have directed their staffs to identify potential funding sources to contribute to the project.

The project has also gained financial support from the county Board of Supervisors ($6 million) and Palo Alto City Council ($3 million).

The county would not provide an updated total cost for the project but past estimates have ranged from $36 million to $48 million.

Facebook's $25 million contribution comes from the company's Teacher Housing Program, which started in 2017 and currently provides 22 affordable housing units for teachers from the Ravenswood City School District in East Palo Alto.

"We're excited to deepen our commitment to housing for people across the economic spectrum," John Tenanes, Facebook's vice president for real estate, said in the announcement. "We hope partnerships like this can inspire other communities to develop their own innovative solutions to providing housing for teachers and other public service professionals, keeping them in the communities that depend on them."

Simitian first proposed the project in January 2018 as a response to the rising cost of living in the area, which local teachers have said is making it increasingly difficult to afford homes close to where they work. A survey on staff housing conducted by the Palo Alto school district found that 59% of respondents (who were mostly teachers) are considering leaving the district within the next five years due to housing costs or long commutes. Unaffordable rental and housing costs are the top reasons that prevent staff from moving closer to work, the survey found.

School districts throughout the Bay Area are either considering or moving forward with teacher housing projects. The Palo Alto Unified school board was set to discuss the topic on Tuesday but postponed due to a long meeting.

Last year, the Mountain View City Council and Mountain View Whisman School District approved a 716-unit apartment complex at 777 W. Middlefield Road, with 144 units set aside for teachers, school staff and city employees.

In August, the county approved two partners, Mercy Housing and Abode Communities, to co-develop the 1.5-acre, county-owned site. Adobe Communities, a Los Angeles affordable housing nonprofit, has experience in bringing workforce teacher housing off the ground.