For Kristin Samadi, a piano teacher and choir director from Brooklyn, the current controversy over transgender people and public bathrooms is not so clear-cut.

On one hand, she takes the view of many New Yorkers: “If a student is transitioning or has already undergone surgery to change their gender, I would be comfortable letting them use the restroom of their choice,” Ms. Samadi says.

But bathrooms, let alone locker rooms or shower facilities, are also places of modesty and privacy, and she might not be so comfortable in certain situations. “If someone enters a female restroom looking masculine, I think it might make a lot of girls uncomfortable – and probably vice versa,” she adds.

On Friday, the nationwide debate over the proper public facilities for transgender Americans reached a crescendo when the Obama administration sent a directive to every public school district in the country, instructing administrators to allow students to use the facilities that correspond to their gender identity.

The move came days after the Justice Department and the state of North Carolina sued each other over a state law that requires people to use the restroom that corresponds with the sex on their birth certificate.

On Monday, United States Attorney General Loretta Lynch told transgender Americans: “We will do everything we can to protect you going forward.”

On Friday, the administration’s directive added that, when upholding civil rights, “the desire to accommodate others’ discomfort cannot justify a policy that singles out and disadvantages a particular class of students.”

The Obama administration’s expansive interpretation of sex and gender promises to reach the United States Supreme Court, experts say. But the discomfort some people feel within public gender-segregated facilities may not always stem from the same kind of prejudice seen in the past and directed against racial minorities or lesbian and gay people, some experts say.

So far, conversations on the issue have been confined largely to conservative Southern states. But in interviews with parents in more-liberal states Friday, the desire to accommodate is still tempered by lingering concerns.

How does this get implemented?

After all, gender-segregated public facilities have been a part of most modern culture, and expectations of modesty and privacy in women’s restrooms, especially, are deeply ingrained.

“For true transgender kids, I wouldn’t have an issue,” says Ian Slade, a health care consultant in Anaheim, Calif., and the father of three daughters now in grade school.

But he worries, too, about what this could mean in practice in public schools. “But for boys being naughty boys, that’s not a good thing for any kids. My issue: How do you prevent that?”

Still, like many in this solidly blue state, Mr. Slade says the Obama administration’s directive “is definitely a step in the right direction.”

“For me, every time we find ourselves at the crossroads of the status quo and equality, history always looks kindly on those that favor equal rights,” he says. “But the mechanics of implementing them is always an issue. How do you safeguard the minority, yet at the same time also keeping the majority in touch, so to speak? How do you do that?”

According to the directive, public school administrators should treat students according to their preferred gender identity if it “differs from previous representations or records” as soon the child’s parent or legal guardian requests it. No medical diagnosis or birth certificate is required.

Many Republicans on Friday accused the Obama administration of overreach. For most supporters of “bathroom laws” like North Carolina’s, sex is a matter of biology and birth, and people should use the facilities that correspond to their gender at birth – or until their birth certificates indicate a full, legal transition.

"This is the kind of issue that parents, schools boards, communities, students and teachers should be allowed to work out in a practical way with a maximum amount of respect for the individual rights of all students,” said Sen. Lamar Alexander (R) of Tennessee, chairman of the Senate education committee, in a statement Friday. “Insofar as the federal government goes, it's up to Congress to write the law, not the executive departments.”

The Obama administration, however, sees the issue as one of basic civil rights protections.

Under federal law, schools must “ensure nondiscrimination on the basis of sex and provide “transgender students equal access to educational programs and activities even in circumstances in which other students, parents, or community members raise objections or concerns,” the directive says.

Who is threatened?

One concern that has been raised in passing “bathroom laws” in Mississippi and North Carolina is that cross-dressing sexual predators could take advantage of such directives and prey on little girls.

But that’s not how Julie Thaxter-Gourlay, an accountant in Port Chester, N.Y., sees it.

“The people who are really in danger in public restrooms are the transgender folks,” she says. “They’re the ones who are assaulted for using the ‘wrong’ facilities. And I would think that transgender children would be the most vulnerable, especially in schools.”

Ms. Thaxter-Gourlay adds that this has been an issue her family has been discussing the past few months. And her conservative father-in-law, she says, “totally changed his mind” on the issue when they talked about how transgender people were actually far more likely to be victims, rather than perpetrators, of violence in public restrooms.

“There’s just no evidence to support the notion that transgender people are assaulting women and children in restrooms. None.”

A number of media organizations and advocacy groups concur. Investigations have found no confirmed incidents of cross-dressing men preying on female victims in bathrooms in the US, with one case reported in Canada.

Online, a number of transgender men and women have posted ironic selfies, showing just how startling they might actually appear in the bathrooms that conform to their sex at birth. Transgender men, born females, often have beards and broader shoulders after undergoing transition treatments, even if they have not had full surgical transitions. Transgender women, born males, can be the most at risk of violence, many advocates say.

A recent CNN/ORC survey found that most Americans oppose laws like those in North Carolina and Mississippi. But there are regional differences.

This week, the Massachusetts Senate passed a bill that would allow transgender people to use facilities conforming to their gender identities. At the same time, however, eight states filed a brief to support North Carolina’s ongoing legal battle with the Justice Department.

“My feeling from our community is that everybody has the right to use what bathroom they want,” says Aileen Cawley, a stay-at-home mom in Los Feliz, Calif., and mother to two daughters, 16 and 10, and a 13-year-old son.

She notes that her children’s private school already has some gender-neutral bathrooms. “But I think there’s been such a backlash against ‘political correctness’ that it’s become the new OK thing to be intolerant of other people and other people’s positions and rights,” Ms. Cawley continues. “There’s fear on both sides ... but everyone’s too busy shouting at each other.”