Federal law prohibits sex discrimination in education programs receiving federal funds. What that means practically is an internal school process with named roles and defined steps.
Every covered school designates a coordinator
Institutions are required to designate an employee responsible for coordinating compliance, and that person's contact information must be made available to students and employees.
The role exists precisely so that a complaint has a destination other than whichever adult a student happens to trust, who may have reporting duties of their own.
Finding that name and title is usually the first practical step, and it is normally published on the district or campus website alongside the applicable policy.
Reporting and formal complaint are different acts
Information can reach a school in many ways, and a school generally has obligations to respond once it knows of alleged conduct.
A formal complaint is a distinct step that initiates a defined process, and students often do not realize they have not started one, or that they have.
Supportive measures such as schedule changes or academic adjustments are typically available independently of whether a formal process is initiated.
The process has stages and both parties have rights
Procedures generally involve notice to both parties, an investigation, an opportunity to respond to the evidence, a determination by someone other than the investigator, and an appeal.
Both the complainant and the respondent have defined procedural rights throughout, and the process is administrative rather than criminal, with different standards and different outcomes.
Retaliation is separately prohibited
Adverse action against someone for reporting or participating is itself a violation, which matters because fear of consequences is the most common reason complaints are not made.
Documentation is what makes a retaliation claim tractable, which is why keeping dated records of communications is worth doing from the beginning rather than later.
The rules change and specifics vary
Federal regulations in this area have been revised repeatedly, and state law and institutional policy add further requirements that differ between districts and campuses.
Anyone dealing with a specific situation should read the current published policy of the institution and consider consulting an attorney experienced in education law.
Campus and community advocacy organizations also provide free support that is independent of the school, and that independence is useful when the process itself is what a student distrusts.