I wish I knew about your book before that horrible summer. Since the attack, I've become a high school teacher and one of my class rules is that all students must place their bookbags against the rear wall. I don't let them keep their bags beside their seats. My reasoning, as I told all my classes, is to keep aisles free of obstacles in case of emergency as well as a safety precaution for normal movement. I also told them it was because I didn't know what each kid brought to school and I wanted to lessen the chance of having a weapon brought out in class.
I don't want to make my kids to think that I don't trust them and that I assume the worst about them, nor do I want to create a negative atmosphere in my class. Am I being too paranoid?
Your rule is also serving as a constant reminder to you of your own anxiety about your attack. Frightening news stories aside, school is still one of the safest places people can ever go. It may be a great lesson to your students if you put an end to the rule and told them you were probably reacting to a violent experience you suffered.
Whatever you do, be sure to give yourself some understanding. You have survived your experience, but full recovery takes time.