Superintendent Parvin Ahmadi estimated the damages at $25,000.
"We are working with the police," Ahmadi said. "We do our part and they do theirs."
Police last week confirmed that juveniles broke in and defecated on computers in the school's library. No one would confirm how the juveniles entered or what other vandalism was done.
None of the juveniles in the case has been arrested, and police will not be seeking charges against them, Sgt. Kurt Schlehuber said.
"It's basically juvenile mischief. The elements of vandalism weren't there," Schlehuber said.
Ahmadi said all of those involved have been taken out of school. No suspensions or expulsions were on the Tuesday night school board agenda, and Adhmadi said, "We're in the discipline process."
Police and school district authorities are also investigating threatening graffiti found on a wall in a girl's bathroom at Pleasanton Middle School. The district warned parents in an email about the graffiti May 30.
"Because this graffiti included a threat toward the school, the Pleasanton Police Department is investigating this incident along with school officials," the district stated in an email.
"The graffiti has been photographed by students and shared with others so there are rumors circulating. We want to assure all Pleasanton Middle School students and families that appropriate precautions are being taken to ensure a safe and secure campus for all students. We will continue to work with Pleasanton PD on this matter," the email said.
It asks any parent or student who might have information about the graffiti to contact the school or Pleasanton police. The district's anonymous tip line is 417-5199, and will accept voice mail or texts. The Pleasanton police non-emergency number is 931-5100.
Schlehuber said police are continuing to investigate the incident, the third in three months.
In March, graffiti at Foothill nearly closed the school, with police, plain clothes officers and school district security swarming the campus.
The Foothill graffiti, which started with an expletive and added, "Watch me shoot everyone on March 14," was written on a girls' bathroom wall Tuesday and quickly photographed by several students who then posted the message on Facebook and other social media.
Later that month, graffiti was discovered at Amador, but it was found at the end of the day and not deemed a serious threat.
No arrest has been made in any of the graffiti incidents.