zipmac22,
There is no law against having your firearm in a vehicle parked on the street. Keep in mind that the school may have disciplinary policies against having a firearm in your vehicle on such streets, and that such disciplinary policies could include being expelled.
If you have a Texas CHL, there is a law that states they should not apply these against you. however, there is no penalty if they break the law, and there is no remedy if you are expelled. So, whether or not this keeps you from being expelled is unknown.
Thanks for the question. Hope that helps.