Defensible? Absolutely not (at least not according to what was reported). Assuming the report is factual, the limited use cited by the schoold district is that once the laptop is reported stolen or missing, the webcam is activated for a still picture.

The kid was called in because the webcam was activated and he was "doing something inappropriate" per the assistant principals words.

Whatever the kid was doing, the fact is that the webcam was activated outside parameters of the stated policy and guidelines. That action cannot be defended. Most people would be very surprised, not to mention horrified to know how often their "public access" systems are monitored....