A Higginsville woman has been charged in a May 15th crash that sent four children to the hospital.  Ashly Pfeifer, 29, slammed into the back of a school bus that was unloading passengers on Business 13 in Lafayette County, according to a Missouri State Highway Patrol crash report.  Pfeifer and her two passengers, Austin Pfeifer, 1, and Ryleigh Thompson, 2, as well as Caylie Moore, 7, of Lexington, and Chelsea Riley, 12, of Henrietta, received minor to moderate injuries.  Pfeifer was charged Tuesday with one felony count of failing to stop for a school bus and two counts of endangering the welfare of a child.  No bond has been set at this time.