Ellen Barry:

Millions of American schoolchildren — close to one-half, according to some industry estimates — are now subject to this kind of surveillance, whose details are disclosed to parents in a yearly technology agreement. Most systems flag keywords or phrases, using algorithms or human review to determine which ones are serious. During the day, students may be pulled out of class and screened; outside school hours, if parents cannot be reached by phone, law enforcement officers may visit students’ homes to check on them.