No, carry is not legal. Unfortunately, a designated school never stops being a school, even when non school-related activities are taking place.
§ 18.2-308.1. Possession of firearm, stun weapon, or other weapon on school property prohibited.
B. If any person possesses any firearm designed or intended to expel a projectile by action of an explosion of a combustible material while such person is upon (i) any public, private or religious elementary, middle or high school, including buildings and grounds; (ii) that portion of any property open to the public and then exclusively used for school-sponsored functions or extracurricular activities while such functions or activities are taking place; or (iii) any school bus owned or operated by any such school, he shall be guilty of a Class 6 felony.