If your parents were in their early 40’s when your sister was born and she’s still in high school, they hardly qualify as “quite old.” 
Your sister can switch public schools but your parents would have to move into the district.
If your parents were in their early 40’s when your sister was born and she’s still in high school, they hardly qualify as “quite old.” Your sister can switch public schools but your parents would have to move into the district.