At the same time, federal investigators have closed a separate disability case against the Palo Alto school district, saying there was "insufficient evidence" that district officials failed to follow the law in looking into a family's complaint.
As part of its investigation in the Gunn case, the federal agency has asked the school for copies of "all complaints of sexual harassment or sexual violence involving students at the school" submitted to the school or district since the start of the 2011-12 school year.
The Gunn case, opened in March and disclosed by the district on May 2, is one of three Office for Civil Rights cases remaining open against the district.
The three include final fulfillment of a December 2012 "resolution agreement" in which the agency found that the district's mishandling of a middle-school bullying case violated the civil rights of a student with disabilities.
The third unresolved case is an examination of school climate and possible peer harassment at Palo Alto High School. District officials said they expect federal lawyers to visit "in the coming weeks" as part of that investigation.
The disability case closed by the Office for Civil Rights last week was the fourth case since last June in which the agency said it had found "insufficient evidence" to support charges against the district.
In that case, a complaint filed last September alleged that the district had failed to implement a written plan to accommodate a student's disability.
After reviewing information provided by the family and the district, Office for Civil Rights investigators said they found "insufficient evidence to support a finding of noncompliance with Section 504 (of the Rehabilitation Act of 1973)/Title II (of the Americans with Disabilities Act of 1990).
"While the student did not agree with the district's conclusion, the evidence did not establish that the district failed to provide a prompt and equitable process for addressing the allegations of discrimination," the federal agency stated in a letter received by the school district April 28. The district released a heavily redacted copy of the letter May 2.
In the earlier cases that were closed after findings of insufficient evidence, the Office for Civil Rights in June said it could not support a conclusion of racial discrimination in the case of a minority student who was searched by school officials in November 2012 after a substitute teacher accused the student of stealing $20 from her purse.
The two other closed cases involved alleged civil rights violations in the handling of bullying complaints by students with disabilities.