Answer:
Mrs. Morningstar refers to the school where William works.
Explanation:
This is from the screenplay Sancho and Bolsa, and it can be found on Scenes 5 and 6. Sancho and Bolsa are detectives, and are working on a missing person case. They are looking for William Morningstar, and they go to Mrs. Morningstar (William´s aunt) house to ask her some questions.
Sancho asks Mrs. Morningstar where does William work, and she replies he works at the White House. Then she explains that The White House is how they call his school. The school´s name is the Martin Alexander Clark School of the Arts.
Next, you can find the portion of the script:
SANCHO Where does William work?
MRS. MORNINGSTAR Now, why don't you be more like Sabado Gigante over here and ask some real questions. William works at the White House.
BOLSA The White House?
MRS. MORNINGSTAR Jumbo, you need to buy your partner a hearing aid. Yes, the white house!
BOLSA The White House?
MRS. MORNINGSTAR No, not the White House. If he worked at the White House, we could afford to hire a real detective to find him. The white house is what we call his school. William worked at a school called the Martin Alexander Clark School of the Arts.