MIAMI — Police have arrested a 15-year-old student accused of making a social media threat against Miami Senior High School, a threat that was then altered by others to affect other schools, Miami-Dade school district officials said Monday. The student is being charged with a felony count of written threats to kill or do bodily harm, said Daisy Gonzalez-Diego, chief communications and community engagement officer for Miami-Dade County Public Schools. For the past several days, Miami-Dade Schools police have been investigating threats made against several schools across the county, mostly on so...