He got a B- grade for designing the current flag of USA.

USA flag facts

17 year old student got b- grade for designing the USA flag.

His Teacher gave him B- grade.
The 50 stars on the USA flag represent the 50 states of the United States of America, and the 13 stripes represent the thirteen British colonies that declared independence from the Kingdom of UK(Great Britan) and became the first states in USA.

The USA Flag has few nick names  like The Stars and Stripes,  Old Glory,  and The Star-Spangled Banner.