If the house bought by grandma is the residence of grandson, that is, grandson and grandma live together, then grandson can enjoy the educational resources of the school district.
If the house grandma bought is not the residence of her grandson, that is, grandma bought herself to live alone, and the grandson doesn't live with her, then the grandson can't study in the school district, because the owner of the school district requires the children to be immediate family members.
The above information is for reference only. Please consult a professional lawyer for specific legal issues.