Baltimore school principals and staff have been threatened with guns, punched in the face, pulled to the ground, kicked and stalked. Some have landed in the hospital. Others have installed cameras and more locks at home. They aren’t afraid of their students. It’s the parents they worry about. “I have never experienced so many adults that are willing to engage in their child’s conflict,” said Craig Rivers, the principal of Frederick Douglass High School in West Baltimore and a longtime city school administrator. “I have never seen it this bad.”