The Walton Family Foundation will give $6 million to the Alliance for School Choice, a group that advocates and lobbies for school voucher programs in states around the country, including Tennessee, the foundation announced Tuesday.

The goal of the investment is to double the number of students who attend private schools with the support of public funds. The Alliance for School Choice says that approximately 300,000 students currently use vouchers to attend private schools.

The Walton Family Foundation, which was created by the family of Sam Walton, the fonder of Wal-Mart, has invested in other education-related programs in Tennessee and nationwide. It helped fund Teach For America in Memphis and a number of charter schools in the state. The Washington Post reports that this donation will double the resources of the Alliance for School Choice. (The Walton Family Foundation is a funder of Chalkbeat.)

Voucher programs have been hotly debated in Tennessee and elsewhere. Supporters of vouchers say the program offers a choice to parents of students who are not happy with their child’s public school. Critics question the effectiveness of voucher programs and say the vouchers drain resources from regular public schools. Some also question the use of publicly-funded vouchers in religiously-affiliated private schools and parochial schools. Most research on vouchers has not indicated that students’ academic performance improves after receiving a voucher.

A spokesman for the Walton Foundation said, “In Tennessee specifically, this investment will support ASC as it works with local partners, parents and schools to drive quality in private schools across the state.”

An effort to extend access to school vouchers  to student from higher-income families and to increase the number of available vouchers in Tennessee failed to pass the state’s legislature last spring.

In Indiana, where the state’s voucher law was expanded in 2011 so that students who do not attend failing schools are eligible, regular public schools have seen drops in enrollment. The Post article also highlights some of the concerns that have come up in Washington D.C.’s federally-funded school voucher program.