Chicago school reform is getting an endorsement from billionaire philanthropist Walter H. Annenberg, who is pledging $49.2 million over five years toward the effort, the largest private gift ever to the Chicago Public Schools.

On Monday, Annenberg's representatives will be in Chicago to announce the grant, which is part of his philanthropic foundation's nationwide effort to improve public education and reduce school violence. The 86-year-old former publisher and diplomat has pledged $500 million over five years to that cause. Annenberg's donation to Chicago is a challenge grant. It must be matched with equal amounts of private and public dollars.

Since Annenberg's school-reform program was announced at a White House ceremony 13 months ago, the philanthropist, through his foundation based in St. Davids, Pa., and his school-reform institute at Brown University in Providence, R.I., has announced grants of $50 million and $53 million, respectively, toward school reform in New York and Los Angeles.