When Texas Lt. Gov. Dan Patrick responded to a school shooting in his state by calling on schools to reduce entrances as a safety measure, advocates of stricter gun laws panned his comments online . . . . But limiting and fortifying entrances to schools has been a school safety best practice since the 1999 shooting at Columbine High School in Littleton, Colo., part of a broader strategy of designing schools to promote visibility of doorways and hallways and to limit access, especially to student-filled areas, like hallways or classrooms, experts said.