New Delhi, Feb. 26 -- In the past few days, nearly every alternate day has brought news of bomb-threat emails sent to one or more schools in Delhi. The script is wearyingly familiar. An email lands in multiple school inboxes-often routed through encrypted servers, sometimes crudely drafted with digital trails left behind. So far, all have proven to be hoaxes. Yet, there has been no let up and the invisible damage they cause continues.

After winter air pollution, which now routinely suspends on-campus classes, these anonymous threats have become the city's other disruptor of education. Each episode may end without physical harm, but the true cost cannot be measured only in cancelled classes, postponed exams or police deployment. It alters...