It’s the kind of stuff that gives moms nightmares: a machete near a play area, household chemicals accessible to preschoolers, and instructors teaching without a criminal background check, the Associated Press reports. These violations and others were found at Head Start centers across the country, according to a report released Tuesday by the inspector general of the Health and Human Services Department. Head Start, the federal program with roots in President Lyndon Johnson’s War on Poverty, provides early education services to nearly 1 million low-income kids nationwide. The federal government gives grant dollars to public, nonprofit and for-profit programs to provide the services. Among the violations found: a screw protruding from a bookcase at child-height level in Longmont, Colo.; a children’s bathroom in Edna, Texas, without lighting for months; and expired infant formula in the refrigerator of a center in the District of Columbia…