Schools under siege

March 1996: Thomas Hamilton shot dead a woman teacher and 16 five- year-olds at Dunblane primary school.

December 1995: London headteacher Philip Lawrence knifed to death after helping a pupil who was being attacked by youths.

June 1994: Man with flame-thrower severely injured A-level pupils in Northern Ireland.

March 1994: Nikki Conroy, 12, stabbed to death by Stephen Wilkinson at Hall Garth School, Middlesbrough.

Summer 1993: Youth with shotgun and machete tried to hold a class hostage at Handsworth Wood Girls school, Birmingham.