Public Schools are not all that interests especially not like those movies where you have mean girls, jocks, nerds, and others.
Since I go to a public school the best I would recommend is to be yourself. Don't try to be someone else you are not because one day you could turn into some you are not use to. School shooting are not common and are especially rare. We have drills that we take to make sure we understand what to do during a school shooting, a fire, or a bomb.
Friends are going to be easy to find if you have common interests with others. However school can be stressful at times because of the homework and the amount of time you have to dedicate your life into it. Just about waking up super early, go to school for 7 hours every day for 5 days straight.
School is fun once you get the hang of it and your friends are going to support you and help you adjust. I have been a new kid before and adjusting to a new school is a really cool experience. Friends would come to you if you accept them. But the friends you choose can change you or help you grow into a better person.