i may be mistaken but according to what i was told in the CCW class i took yesterday possession of a firearm is prohibited completely on school grounds. that includes the parking lot and any grounds associated with the school. the statute also includes private schools and universities. so to answer your question, no it is not legal to leave the weapon in the car because it is still on school property. if somebody knows otherwise please let me know. i occasionally have to pick my little brother up from school and worry about what to do with my pistol.