In a story, can you make up a place and put it in a real city?

For example, if I was writing a story, could I make up a place like, let's say, Marshmallow Hill High School and put it in Miami, even though there is no such place in Miami? I know if the plot of the story takes place in the future, then it would be fine, but what about the past or present? In a book I have read, the author made up a school and put it in her story, but is that actually okay to do? I know I probably sound like an idiot for asking this question, but and help would be much appreciated. Thank you!

(P.S. Please, do not answer this question if you aren't sure)

If it is a narrative you can make up a place and put it in a real city or make up something really fake, you can do that but if it is based on fact than you can't.