Analysis Finds Gains in Edison Schools, But Model Is No Quick Fix

Edison Schools Inc., the nation’s largest for-profit manager of public schools, is posting achievement gains that are on par with, and sometimes exceed, the gains made by students attending comparable district-run schools, a study released last week concludes.

But the study, conducted for Edison by the Santa Monica, Calif.-based RAND Corp., found that it took Edison schools at least four years to match or exceed those average achievement gains in reading and mathematics.

And for “conversion schools”—previously run by a district and turned over to the company to manage—student achievement dropped during the inaugural year. It took five years, RAND found, for conversion Edison schools to post test-score gains that at least matched...