The mayor of Providence has gone back to school to read to students as part of a national effort to break the record for the most people reading the same book in one day. Mayor Angel Taveras and the city’s school superintendent read the children’s book ‘‘Ladybug Girl and the Bug Squad’’ to kindergartners at Spaziano Elementary School Thursday. Taveras also read the book in Spanish to a bilingual class. The visit was part of a national effort to promote early reading. Organizers expect 2.5 million children across the nation to take part in the event, which they hope will set a world record for most people reading the same book on a given day.