This is an interesting article on physical restraints. It emphasizes the universal protocols and policies relating to the last possible action to be considered when interacting with an unruly student.
Although specifying the usage of a non intrusive technique, it fails to assess the possibilities of injuries and trauma also experienced by staff.
The student population describe appears to me as a population that experienced high levels of stress with different levels of experiential trauma. The excerpt that cites the challenges associated with the responsibility linked to provide education and to manage the classroom is one that needs to be addressed by further exploration. Fire drills are practiced more frequently that crisis ones!
It is also important that we factor in the impact of having ill equipped and unprepared teachers respond to very complex challenges. I am not criticizing teacher's competences but rather doubting that they feel confident in managing these issues.
Read the article in The Lowell Sun: Student restraints only raise a question society must answer