Yes: openly carried handguns are permitted on school property except when school sponsored activity (Athletics, Band, and ROTC) practices are taking place in those locations.
School property is defined as the exterior of a school building such as sidewalks, parking lots and driveways.
PC 36.06 Concealed Carry and PC 36.07 Open Carry, if proper signage is posted, an individual who is in violation can be charged with Criminal Trespass.
Note: handguns are prohibited whether concealed or openly carried inside the school building.