South Dakota would be the first state in the U.S. to approve a law requiring transgender students to use bathrooms and locker rooms that correspond to their sex at birth if the governor signs a bill passed Tuesday by the state Senate.

The Senate voted 20-15 to send the bill to Republican Gov. Dennis Daugaard, who initially responded positively to the measure but said last week he'd need to study it more before making a decision.

Advocates say the bill is meant to protect the privacy of students, but opponents say it discriminates against vulnerable adolescents.

Under the plan, schools would have to provide a "reasonable accommodation" for transgender students, such as a single-occupancy bathroom or the "controlled use" of a staff-designated restroom, locker room or shower room.

Republican Sen. David Omdahl urged other legislators Tuesday to support the bill to "preserve the innocence of our young people."

Democratic lawmakers and some Republicans unsuccessfully opposed the measure in the Senate.

The American Civil Liberties Union of South Dakota and Human Rights Campaign have been vocal in their opposition to the measure and have called on Daugaard to veto the legislation.

"History has never looked kindly upon those who attack the basic civil rights of their fellow Americans, and history will not treat kindly those who support this discriminatory measure," Chad Griffin, the president of the LGBT-rights organization Human Rights Campaign, said in a statement Tuesday.

Transgender advocates have also criticized comments made by some lawmakers, including Omdahl, about transgender people.

"I'm sorry if you're so twisted you don't know who you are," Omdahl said at a recent event when asked about the bill. "I'm telling you right now, it's about protecting the kids, and I don't even understand where our society is these days."

There is no evidence to suggest that people who are transgender use entry into bathrooms associated with their gender identity to harm children. A trans student in Maine and her family were awarded $75,000 in a discrimination lawsuit after her school required her to use a staff bathroom instead of the girls' room, and she's not alone.

“Sen. Omdahl’s name-calling shows he really doesn’t know where society is right now ... This bill will expose schools to significant lawsuits they simply can’t afford," said Executive Director, Mara Keisling of the Nation Center for Transgender Equality. "Hopefully the Governor understands that, and will use his veto power to protect all of South Dakota’s students and schools.”

See also: The faces of transgender teen America

In Oklahoma, a similar bill that would require students to use the restroom corresponding to their biological sex has been referred to the state's office of Health and Services for consideration.

A man urges people to vote against the Houston Equal Rights Ordinance outside an early voting center in Houston in October. Image: Pat Sullivan /Associated Press

In Houston, Texas, last November, a fierce campaign that used the slogan "no men in women's bathrooms" was successful in turning voters against HERO, a city ordinance that included "gender identity" as one of fifteen "protected characteristics" against discrimination. HERO, which stands for the Houston Equal Rights Ordinance, had originally been approved by the city council but was eventually struck down by the Texas Supreme Court, which ruled that anti-discrimination protections must be put before voters.

Meanwhile, religious advocacy groups, such as a statewide coalition called Privacy for All, have repeatedly tried to halt measures in California that allow transgender people to use bathrooms that match their gender identity, although they have been largely unsuccessful.

Despite the activity in other states, however, South Dakota would be the first in the nation to put a measure into law banning transgender or gender nonconforming students from using the bathroom of their choice, said Joellen Kralik, a research analyst at the National Conference of State Legislatures.

"...it does more harm than good to both trans kids and South Dakota’s reputation," said Keisling.

Students have expressed outrage that the bill has been able to get this far without being struck down.

The Legislature's passage of the bill is "shocking," said Thomas Lewis, a transgender student in his senior year at Lincoln High School in Sioux Falls, the state's most populous city.

"At this point, I'm hoping that the governor has a sense of humanity and the common sense not to write this bill into law," said Lewis, who is planning to attend college in Minnesota. "I am so glad to be leaving soon. I can escape the oppression that my home state wants to put on me."

Supporters say South Dakota's plan is a response to changes in the Obama administration's interpretation of the federal Title IX anti-discrimination law related to education. Federal officials have said that barring students from restrooms that match their gender identity is prohibited under Title IX. Many public universities have already begun the process of transforming public restrooms on campus into gender nonspecific facilities.

Daugaard has five days to sign the law into effect. He announced Thursday that he would be meeting with transgender students and allies before making a decision.

Additional reporting by Gillian Edevane.