It took a private donation worth thousands of dollars from an anguished mother to pay off school lunch debts of seniors at a Minnesota high school — and the gesture has kickstarted a conversation about protecting students from punitive debt collections.

A coalition of elected officials and legal advocates want to make it the law that a student cannot be denied a diploma or a spot on a sports team over a lunch debt.

The story of how Valerie Castile, mother of police shooting victim Philando Castile, recently paid $8,000 in honor of her son so seniors at Robbinsdale Cooper High School in New Hope could graduate without debt generated national headlines. Some versions of the story said the school would withhold diplomas until the debts were paid, but a school spokeswoman said Friday that that was never the case.

Castile's son, who had been a cafeteria supervisor at a St. Paul elementary school, frequently paid for lunches for students, his family has said. The Philando Castile Relief Foundation has also helped pay lunch debts in the St. Paul school district.

But it isn't entirely a feel-good story for Mid-Minnesota Legal Aid attorney Jessica Webster, who for years has decried the practice of shaming kids over unpaid lunch bills.

Alarmed by the Robbinsdale Cooper example, she's pushing for a formal opinion from state Attorney General Keith Ellison's office that would spell out legal protections for students with lunch debts.

State law already prohibits school districts from withholding diplomas for nonpayment of fees, and Webster said Legal Aid attorneys believe that should include school lunch debt.

"In our view, graduation is … something that students have earned, and they shouldn't be denied that based upon an inability to pay a lunch debt," she said. "These are the legal arguments. There's also a moral argument. This is really cruel."

The practice of punishing students for unpaid school lunch bills has long been unpopular among many Minnesotans. A push several years ago led to a 2014 law saying schools could not "demean or stigmatize" a student while reminding them of a debt.

This year, several legislative efforts to add specifics to that law are underway.

A House bill sponsored by Rep. Tony Jurgens, R-Cottage Grove, requires schools to provide a meal in a respectful manner. It also gives the state education commissioner some enforcement authority. A companion bill in the Senate was introduced by Sen. Susan Kent, D-Woodbury.

The bills say districts cannot dump a student's meal or put stickers on a child when school lunch bills go unpaid, practices in recent use in at least one Minnesota school district.

Webster said she's heard of no opposition to the school lunch legislation, but a similar bill failed to pass last year even though it had widespread bipartisan support. It was included in a larger package of bills that Gov. Mark Dayton vetoed for unrelated reasons.

Webster has also called on Education Department Commissioner Mary Cathryn Ricker to pursue districts that have written policies allowing for punitive measures against indebted students.

To examine district policies, Legal Aid attorneys sent out public records requests two years ago to every Minnesota school district. Some districts didn't respond, and some had nebulous language, but at least four — Roseville, Mahtomedi, Floodwood and Kelliher — had written policies that Legal Aid attorneys considered illegal.

At least two of those districts have already rewritten the problem policies. Mahtomedi Superintendent Barbara Duffrin said that when she took office last year she noticed a policy that allowed the district to pull a student out of sports or field trips over unpaid fees, and she asked that it be updated.

"I saw it as a problem," she said, adding that no one wanted to keep the rule.

A spokesman for Roseville Area Schools said a student guide last year included warnings that some privileges, including receiving a cap and gown, could be suspended for unpaid debts. That's not the case this year, said spokesman Josh Collins. "It's illegal," he said, adding that Roseville did not invoke the punishment last year even though it was in the student guide.

Ricker wants an end to lunch shaming as well, said Education Department spokeswoman Wendy Hatch.

"The commissioner has been working on lifting barriers for all students to participate in graduation ceremonies," she said. To strengthen state law on the matter, Ricker met with the governor's office about legislation, making it "crystal clear" that a student can participate in graduation ceremonies regardless of any school lunch debt.

The new legislation could finally put an end to stories like the one out of Stewartville last year. There, some 143 hot entrees were removed from students' lunch trays and thrown into the trash, sparking a public outcry.

Webster said one of the lessons from that episode was that the law doesn't include any mechanism to enforce schools' compliance.

"That's why we've engaged the attorney general, because it's a little unclear how this can be enforced," she said. School districts have other ways to get the bills paid, including using debt collectors, she said.

"We just don't want the child in the middle of it," she said.