Beavercreek is about as safe as you can get. There's the occasional vandal, but the police force does well to curb any petty crime. Most crime is theft from the malls anyways.
The high school is rated excellent by Ohio's Report Card system. Having been there, I'd say it is pretty friendly. Are their cliques? Sure, but it is such a large high school (5th in the state) that most kids find a group that fits them. I recommend going out for extracurriculars and honors classes.
Here's the city's website.
Welcome to the City of Beavercreek