BROOKLYN CENTER, Minn. – The Minnesota State High School League voted overwhelmingly to adopt a new transgender student athlete policy that has infuriated conservative groups and stirred heated debate in recent months.

League board members voted 18-1 with one member abstaining to adopt a formal policy that requires public schools to allow transgender students to play on sports teams based on their gender-identity, rather than their birth gender, the Minneapolis Star-Tribune.

Girls are already permitted to play on boys’ sports teams in Minnesota, but the new rules allow boys who identify as girls to play on girls’ teams, which has prompted concerns about transgendered boys using female locker room facilities and complaints about an unfair physical advantage.

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“When there is confirmation of a student’s consistent and uniform gender-related identity…the student will be eligible to participate in MSHSL activities consistent with the student’s gender identification for the balance of the student’s high school eligibility,” according to the new policy, quoted by Fox News.

According to a tweet from the league’s media representative, “Minnesota will become the 33rd state to implement a policy for transgender high school athletes,” the news site reports.

The policy was adamantly opposed by the Minnesota Child Protection League, the Minnesota Family Council and others, while the National Center for Lesbian Rights, OutFront Minnesota, and other LGBT advocates championed the measure.

League board members approved the new transgender policy at a packed meeting in Brooklyn Center Thursday after about 20 speakers on both sides of the issue voiced their opinions, including transgender students, spokespeople for advocacy groups, and lawmakers. Many who attended waved signs throughout the meeting, from “We do not support the policy!” to “I love my trans friends and family,” the Star-Tribune reports.

The board received tens of thousands of emails on the issue beforehand, and the Minnesota Child Protection League took out two full-page ads leading up to the meeting calling the policy “The End of Girls’ Sports?”

“The ad shows a brunette softball player resting her head on a bat, as though she was benched, with the caption, ‘Her dreams of a scholarship shattered, your 14-year-old daughter just lost her position on an all-girl team to a male…and now she may have to shower with him,’” Fox reports.

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“A biological male has a larger skeletal structure, more muscle. Generally speaking this is true,” Michelle Lentz, state coordinator for the Minnesota Child Protection League told Minnesota Public Radio. “To put them in a position where they are competing against girls, puts those girls in a situation where they could get hurt.”

That was the same argument made by attorney John Hagen in a column for the Star-Tribune. Hagen also argued the policy could result in lawsuits because it requires schools to gauge the sincerity of students’ gender claims.

“Imagine the following scenario,” Hagen wrote. “An adolescent counterpart of Clay Matthews (the very long-haired, very burly linebacker for the Green Bay Packers) comes before your school board. He declares: ‘I always have had a feminine self-image. I never told anyone, because of society’s expectations, but I’m revealing it now. My long hair is evidence of my sincerity and my feminine self-expression.’

“The High School League’s … policy would compel the school to let this boy play power forward on the girls’ basketball team, regardless of safety considerations. (Imagine a Clay Matthews look-alike bowling girls over under the basket.) If the school resisted, it would promptly be faced with a lawsuit under the ‘will be eligible’ clause.”

The new policy applies to nearly 500 public schools that hold a membership with the Minnesota State High School League, but doesn’t apply to private schools.

A proposal presented by the Minnesota Family Council to require a student’s birth sex to be used to determine eligibility, a measure backed by more than 5,500 people from 28 public and private high schools, was not considered at the Thursday meeting.

Family Council director of legislative affairs Autumn Leva told the Star-Tribune those who backed its proposal were “excluded from the discussion.”

Only one member of the State High School League Board, St. Cloud Cathedral activities director Emmett Keenan, voted against the transgender policy, according to media reports.

“ … I’m not sure we’ve heard enough yet about the safety of girls in relationship to a transgender male-to-female playing on girls’ sports teams,” he said.