LONDON — Last month, filmmaker John Sweeney traveled with a group of students from the prestigious London School of Economics (LSE) on a government-sanctioned tour of North Korea. Sweeney’s resulting 30-minute documentary on the secretive, oppressive state aired Monday night on the BBC’s Panorama program. LSE staff and students, however, say that Sweeney and his colleagues misled the students about their intentions. They claim the filmmakers used them as “human shields” for otherwise prohibited journalism without their knowledge or consent — a claim the filmmakers protest — and that the BBC’s actions endangered the students, the school and the future of such visits for all institutions.