In the aftermath of last month’s mass shooting at Sandy Hook Elementary School, some private schools are questioning whether it is appropriate to accept grants from the Walton family, whose Wal-Mart chain is the country’s biggest gun seller, Bloomberg writes.

The Walton Family Foundation is biggest private donor to charter schools, with $312.9-million in support since 1997. Wal-Mart, of which the Waltons own 48 percent, has come under pressure to restrict firearms sales since the December 14 massacre in Newtown, Conn.

“It’s a moral issue,” said Andrew Sweigard, principal at the Academy of New Media Middle School, in Columbus, Ohio, which has relied on a $250,000 Walton foundation gift to stay open. “Can we take funding from a company that is linked to a potential disaster in our school? Do we want to associate ourselves with guns?”

A Wal-Mart spokesman declined to comment specifically on schools’ concerns. Richard Moreno of the Charter School Services Corporation, an umbrella group that received more than $1.6 million from the Waltons in 2011, drew a line between the foundation’s philanthropy and the firm’s gun policies, which he said is “a decision for the shareowners.”