Gloria Laniece Bryan was desperate to see the boy after falling out with his parents, according to Iowa City Press Citizen.
The 66-year-old, who was allegedly pretending to be an old man and had a walking frame, found her grandson in the Iowa City High school cafeteria, police said.
She was then said to have handed him a toy and some sweets, but fled after staff quickly identified her.
Bryan reportedly admitted disguising herself and told police she was ‘desperate to see him’ when they apprehended her last Thursday.
The grandmother was charged trespassing and third-degree harassment.
The child’s mother is now apparently asking for a protection order against Bryan.