William Bennett, who resigned as Ronald Reagan's education secretary to return to private life, says he can't fully explain why he agreed to be George Bush's drug fighter. But he begins by recounting the fears of two urban mothers.

"One told me that she believed the schools were improving . . . but that she was afraid to send her child to school . . . because of the drugs and violence," Bennett recalled in a speech preceding his Senate confirmation hearings this week."Another told me she gives her child money . . . to give to drug peddlers and then instructs her daughter to throw the drugs away . . . because if she doesn't buy from pushers they will beat her up," he said.

The stories of inner-city anguish were told to the U.S. Conference of Mayors as Bennett prepared his case for the Senate Judiciary Committee. Senators will hold hearings Wednesday and Thursday to weigh his nomination to be director of the new Office of National Drug Policy Control.

"I volunteered for this job," Bennett told the mayors. "I can't tell you exactly why, except to say I (was moved by those mothers). I think they probably had something to do with my volunteering."

Bennett, 45, is expected to take his passionate, blunt approach to problems to a job that is especially suited for it. His chief task will be to bring order and direction to what has been a fragmented federal anti-drug effort.

Bennett did not promote unity as Reagan's controversial education secretary, and last year he broke with Reagan's administration to call for a greater role by the U.S. military in narcotics interdiction.