At Ford High School in Detroit, students and staff members see the school year in two parts: the month before 16-year-old Christopher Walker was gunned down outside the school and the 2 1/2 months since. Before the Oct. 16 murder -- the first at a Michigan school in eight years -- fights occurred almost daily, gunshots were fired in the parking lot at least once, and rival gangs vied for respect. There are fewer brawls now because no one wants to die like Walker did -- in a hail of gunfire that witnesses and police said resulted from a fight in the halls. Some Detroiters -- police, politicians, pastors and program leaders -- have begun putting up a fight to turn around the perception of the school and make it feel safe. Staff members have been assigned to mentor several students. An antiviolence program called Second Step has started.