Fourteen-year-old Tina Faelz disappeared on April 5, 1984, while walking home from Foothill High School.
She was found stabbed to death in a drainage area adjacent to Interstate Highway 680 late that afternoon, police said.
The area is located east of the high school campus, and at that time it was undeveloped and was frequently used by students walking to and from school, police said.
Although Pleasanton Police Chief Dave Spiller announced the arrest at a news conference today, he declined to release the suspect's name because he was a juvenile at the time the crime was committed.
However, his name could be released after he is referred to adult court, Spiller said.
Pleasanton police said that when Faelz's body was discovered, they conducted exhaustive crime-scene processing and interviewed classmates, friends, school faculty and nearby residents.
Officers searched the area but didn't find a suspect or a murder weapon, police said.
Police said that in the 27 years since the murder, they kept the case open and investigated any tips or new information that emerged, but it remained unsolved.
In late 2007 they again reviewed the physical evidence that was collected in 1984, taking into consideration scientific analyses that might not have been available at the time of the murder. Items were submitted to two different laboratories for evaluation and examination.
Last October, the FBI crime lab in Quantico, Va., provided information to Pleasanton police that led to the suspect's identification.
The case has been forwarded to the juvenile division of the Alameda County District Attorney's Office for review and charging.
Spiller said in a statement, "It is very gratifying to have the many long hours our department has invested into this case result in some possible closure. It has been very hard on the family of the victim and the community, which was devastated that this caliber of crime occurred here."