COLUMBUS, Ohio (AP) - Authorities looking into alleged fraud swept across the Columbus City School District on Thursday, seizing records from several high schools and perplexing district officials who said they have been cooperating with the state auditor's investigation.

State and federal authorities are investigating Ohio's largest school district over allegations that employees improperly altered the grades or attendance records of struggling students to improve performance ratings in a process called "scrubbing."

Ohio Auditor Dave Yost's office said 34 warrants involving 20 schools were executed. Those included Marion-Franklin, Whetstone, Mifflin, Independence, Linden-McKinley and Northland high schools.

Spokesman Jeff Warner said the district was surprised by the searches.

"The district and our schools are fully cooperating with authorities seeking these records," he said.

Superintendent Gene Harris first sought a special state audit in 2011, but Yost initially declined her request. After intense public scrutiny and a renewed request by Harris, Yost launched the investigation in June.

Warner said the district has provided "hundreds, if not thousands" of student records of the same type sought by the search warrants during the ensuing 10 months.

The warrants came the same day Yost testified before state lawmakers on a state budget provision creating a new type of academic distress commission capable of taking over a district where an attendance-tampering investigation uncovers intentional deception. A coalition of community, religious and labor leaders protested the plan outside the nearby Ohio Department of Education headquarters.

Yost launched a separate statewide review of school district attendance and enrollment tracking changes based on early findings in Columbus and districts in Toledo and suburban Cincinnati. His auditors fanned across the state to investigate a sampling of districts identified through a statistical analysis.

That separate probe found nine Ohio districts that intentionally removed poor performing students from their rolls and discovered that more than 70 schools or districts had attendance reporting errors that didn't appear to be purposeful.

Federal authorities joined the Columbus schools investigation in November and Yost separated it from the rest of his state probe because of what he described as a likelihood of criminal referrals.

The practice of scrubbing has drawn attention across the country amid greater scrutiny of the increasingly data-driven world of public education. Its temptations include rosier district report cards, added state or federal funding and employee bonuses.

A former superintendent went to prison in Texas for conspiring to remove low-performing students from classrooms to boost average test scores. Principals in Oklahoma and Missouri also are out of their jobs after attendance-related scandals.

Three key individuals connected to the Columbus data manipulation controversy have left their jobs at the district's urging since the investigation began. Harris has announced she will retire at the end of this school year, a move her supporters have said is unrelated to the ongoing investigation.

Also Thursday, a judge ruled that the Columbus school board can't legally close its meetings to the public simply by having an attorney in the room and claiming attorney-client privilege.

The Columbus Dispatch had challenged the claim, saying the board was circumventing Ohio's open meetings laws as members discussed the attendance data scrubbing scandal.

Franklin County Judge Julie Lynch upheld a magistrate's February ruling that the board must stop such meetings, a tactic the newspaper said was used to close seven meetings last year.

The district declined to comment on the judge's decision.

The case is set for trial in the fall. The newspaper is seeking a permanent injunction stopping such meetings and payment of its attorney fees.