When i went to High School in central Florida 40+ years ago, it was not against school rules to to have rifles in your vehicle on the the school parking lot. Many students went hunting after school. I have no idea what the current regulations are.
Sadly freedom has been stolen from us by murderous idiots domestic and foreign. States and schools have “no firearms or weapons” policies, plus gates, metal detectors, and guards to enforce them.
Note that the cow killers had a handgun as well as a rifle — they were on foot and thus had no vehicle to lock their guns in during the school day. I find them guilty and sentence them to 50 years in prison — don’t need no stinkin’ evidence. (Joking, sort of)