Benjamin Franklin High School is a
public high school. Public high schools in the United States don't generally issue diplomas by mail *as the primary method*. Diplomas are typically awarded in a formal ceremony and then provided to the student directly after graduation or through the school's administration in person or via secure delivery.
If a student has graduated from Benjamin Franklin High School and hasn't received their diploma, they should contact the school's administration directly. There may be a legitimate reason for a delay, but sending a diploma via regular mail is unusual for a public school. They'd likely use a more secure method.