Dead threats, serious or not, should not be taken lighty, there's been way too many episodes in America about kids killin' others at school.
Not disagreeing that death threats shouldn't be taken seriously, but actually very few students are killed in school every year. In the 60's the numbers were around 50, but they've gotten consistently less and less as time went on. I believe even when Columbine occurred, the number still decreased from the year before.