Why It Matters: The lawsuit puts other districts on notice.

The Chino Valley Unified School District in San Bernardino County recently began requiring that parents be notified when their child asks to use a name or pronoun that does not align with the child’s birth certificate, or seeks to use a bathroom assigned to a different gender.

Mr. Bonta is seeking not only to stop that policy, but also taking aim at three other districts in California that are trying to follow suit. The attorney general, a Democrat, said the policies amounted to the “forced outing” of transgender students.

Although the number of young people who identify as transgender in the United States remains small, it has nearly doubled in recent years, and schools have come under pressure to protect the privacy and safety of students who are changing their gender identities. This has led to backlash from conservative groups, as well as from some parents who say that such protections infringe on their own rights to know what their children are requesting at school.

Background: The issue has become contentious even in parts of California.

The issue has inspired conservative legal groups to file a number of lawsuits against school districts across the country and has prompted a campaign by religious conservatives to promote “parental rights” candidates for nonpartisan local school board seats. In California, a state dominated by Democrats, only a handful of districts have pursued policies similar to the one enacted by Chino Valley Unified, which serves suburbs about 40 miles east of Los Angeles.

The other districts include Anderson Union High School District in Northern California and the Murrieta Valley and Temecula Valley school districts in the Inland Empire.

The Chino Valley school board approved its policy during a contentious meeting in July in which the state superintendent of public instruction, Tony Thurmond, was ousted from the board chambers after he criticized the measure. The Chino Valley school board president, Sonja Shaw, rebuked Mr. Thurmond at the meeting and charged that the state’s liberal leaders were “pushing perversion on our children in every possible way.” Ms. Shaw, who was elected last year, is the effort’s most vocal backer.

What’s Next: An initial court decision could come within days.

Mr. Bonta filed his lawsuit in San Bernardino Superior Court asking for a temporary injunction against the Chino Valley policy and seeking a permanent order blocking it. He argues that the policy violates the California Constitution because it discriminates against transgender students, denies their right to education and violates their right to privacy.

He said at a news conference on Monday that he expected a hearing this week on his injunction request.

In a statement, Mr. Bonta said that the Chino Valley policy “wrongfully endangers the physical, mental, and emotional well-being of nonconforming students who lack an accepting environment in the classroom and at home.” The lawsuit, he added, serves as a “message” that “we will never stop fighting for the civil rights of LGBTQ+ students.”

“Bring it,” Ms. Shaw retorted in a text message to The New York Times on Monday. “This is another ploy to stop all the districts around California from adopting a common sense legal policy. We will stand our ground and protect our children with all we can because we are not breaking the law.”