The study by the Brown Center of Education Policy compares the rankings of 1,156 public schools in California in 1989 with their rankings in 2009.
LAUSD Superintendent Ramon Cortines says he's taking steps to help underperforming schools, such as Roosevelt High, improve.
"I put Roosevelt on notice two years ago. They made a slight improvement this past year. I believe they will do better this coming year because they're going to be on single track and they're not going to have as many students on that campus, and it's not going to be a sardine can," Cortines said.
John Rogers, co-director of University of California Los Angeles' Institute for Democracy, Education and Access, noted that 20 years is a long period in which to look at a school's performance.
"There was a rapid decline in conditions in California schools during this time, we had a lot of overcrowding, a lot of teachers lacked a credential," Rogers said. "Budget cuts have eroded any improvements."
Another report found that campuses didn't show significant academic gains after they were converted to charter schools.
The Associated Press contributed to this story.