We had one two years ago, i was sleeping in spanish when the principal came onto the intercom "teachers if you see anything unusual in your rooms please let me know" then i fell back asleep and then he came back on again "we have a bomb threat and we need to evacuate the school". The the whole school bailed and we sat in a church by the school for 2-3 hours until my dad finally came and signed me out, and literally 5 mins after i left everyone had to go back to school, it was great.