Outbreaks of Violence at USA and Canadian Schools (a list of some major violent incidents in North American Schools - May 1975-April 16, 2007). Canada

USA school shooting kills 33 (alleged shooter kills self) & How schools can keep students safe? (build elaborate 'security' systems). BBC, Apr 17, 2007
Few campuses have elaborate security, but experts suggest the following options could help keep staff and students safe
1) Wall provides secure perimeter and stops public entering campus
2) Security guards control access, with ID cards used by staff and students. CCTV cameras record movements of people and cars
3) Control room provides airport-style checks and acts as base for 25-30 campus police at typical college. Security systems monitored
4) Key buildings including labs and dorms have own security guard, CCTV and swipe card entry. Forced entry raises alarm
5) Tannoy system/siren conveys key information or raises alarm
6) Texts, automated phone calls and e-mails from control room warn students and staff of emergency and keep them updated

Gunman attacks a Canada College (wearing black trench coat, military boots, Mohawk haircut, emotionless as he fired his weapons). BBC, Sep 14, 2006

1st day for police in schools ("they'll be doing a lot more than just patrolling the halls"). WLNX Pheonix News, Sep 6, 2006
It's the first day of classes for many students, but there's another first for some Lansing school children - the presence of police in schools...."Just patrolling halls, seeing if there are any kids out that should be in class." He got a formal introduction to students. "I was standing in the back, she introduced me, that didn't go too well, a lot of the kids booed." District officials say a permanent police presence in high schools will keep disruptive activity away from the classroom....As of now there are four police officers in all four of Lansing's high schools, and in the coming semesters, they'll be doing a lot more than just patrolling the halls. Liaison officers are putting together mini classes for students on some major topics - "Sexual harassment, hate crimes, gangs, the courts, how the court system works." But before those courses get underway, liaison officers are still trying to help students find their core classes.