WASHINGTON — The Supreme Court on Tuesday upheld state laws barring transgender girls and women from playing on school athletic teams, in another setback for transgender people.

The court’s six-justice conservative majority, which has repeatedly ruled against transgender Americans in the past year, ruled that state bans in Idaho and West Virginia don’t violate the Constitution. The court unanimously agreed that barring transgender girls and women also doesn’t run afoul of the federal law known as Title IX, which prohibits sex discrimination in education.

Justice Brett Kavanaugh wrote for the court that, “states may maintain women’s and girls’ sports for biological females” to address safety and competitive fairness concerns. “The Constitution and Title IX do not require an overhaul of women’s and girls’ sports throughout America.”

More than two dozen other Republican-led states have adopted bans on female transgender athletes, and the decision seems certain to extend to them as well.

Left unresolved by the outcome are lawsuits challenging state laws and regulations in Connecticut, California and elsewhere that permit transgender athletes to compete consistent with their gender identity.

Justice Sonia Sotomayor dissented, saying from the bench that the majority opinion was wrong to reject an equal-protection claim from 16-year-old Becky Pepper-Jackson.

With the science still evolving, transgender students shouldn’t automatically be shut out of team sports, she said. “We just simply do not know scientifically that transgender students pose dangers,” she said, reading from a dissent joined by her liberal colleagues.

Pepper-Jackson, a high school sophomore in Bridgeport, West Virginia, has been taking puberty-blocking medication, has publicly identified as a girl since age 8 and has been issued a West Virginia birth certificate recognizing her as female. She is the only transgender person who has sought to compete in girls sports in West Virginia.

About 2.1 million adults, or 0.8%, and 724,000 people ages 13 to 17, or 3.3%, identify as transgender in the U.S., according to the Williams Institute at the UCLA School of Law.