SACRAMENTO (AP) — Much of the funding for pro-school choice groups and candidates in California comes from a handful of wealthy donors.

Analysis of top donors to school-choice ballot measure campaigns around the country found 48 individuals and couples provided most of the reported contributions to those initiatives since 2000.

READ MORE: Volunteers Spread Out Across Bay Area for Annual Coastal Cleanup

Some of those top donors are major backers of pro-school choice candidates in California. Several are already pouring money into 2018 campaigns for governor and state schools chief in California.

Top California school choice donors include Netflix founder Reed Hastings, Gap founders Donald and Doris Fisher and KB Home founder Eli Broad. Members of the Walton family that founded Wal-Mart and former New York Mayor Michael Bloomberg have also contributed millions to California school choice groups.

Thirty states plus Washington, D.C., have some combination of vouchers, government-subsidized education savings accounts or tax credits that help families afford private-school tuition or encourage private groups to fund scholarships, according to EdChoice, an advocacy group founded by Friedman and his wife.

READ MORE: San Francisco Celebrates Rise of Lowrider Community With Car Show and Cruise

Still, less than 1 percent of children in kindergarten through high school used vouchers to attend private schools in 2015. Just 5 percent of students were in charter schools that year, when charters were operating in more than 40 states. That’s up from about 3 percent in 2008, according to the Department of Education.

Charter schools are public but in several states are not held to the same accountability standards as traditional schools, which in theory gives them more freedom to innovate.

When standardized test scores of children who switched to charter schools or used vouchers are compared with those of students who remained in traditional public schools, some results have been promising. Other studies have shown little effect or even worse outcomes.

MORE NEWS: San Francisco Schools, Public Health Dept. Partner to Provide Campus COVID Vaccinations

© Copyright 2017 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.