What kind of laws are there in Virginia regarding school attendance of minors?

I’ve tried googling this, but my google-fu appears to be failing me, and I really need an answer. Can anybody help?

My sister is in an abusive relationship, and currently her husband isn’t allowing her to use the car. For ANYTHING. He says if she drives it, he’ll call the police and report it stolen and have her arrested. This means she can’t bring my nine-year-old nephew to school, and her husband won’t do it, either. The school is a private school and doesn’t provide transportation. Laws vary from place to place, but isn’t it generally illegal for a parent to prevent their school-age child from going to classes when they’re not ill?