have you ever encountered any security threat while on campus?

Are you asking about high school or college?

In high school we only ever had one incident, where some smooth brain brought a gun to school. They got into big trouble and it was a minor scare but ultimately didn't work out to much.

From what I hear in college, security incidents are a thing but aren't too common. Most colleges don't have a lot of violent crime, but petty theft can be common in some places. Colleges do have security and sometimes even their own mini police forces, and they are generally well lit and are plenty safe. As long as you go with somebody at night and don't actively seek out trouble (ie parties, drugs), 99% of the time you're going to make it through college or at a bare minimum live to tell the tale.