Forty-five million. That’s how many plastic straws Miami-Dade County Public Schools was sending to landfills every school year, according to estimates by administrators. This school year, that number is zero. Starting last August, the district eliminated plastic straws from the utensil packets distributed during breakfasts, lunches and after-school meals. Now, students get sporks and napkins, and those who need straws can ask for the paper variety. It’s one in a series of steps the nation’s fourth largest school district has taken to become more environmentally sustainable. With 345,000 students and 40,000 employees, simple policy changes can make a big difference. Five years ago, the district swapped out polystyrene foam lunch trays for compostable paper plates. After that, a high school student from MAST Academy started a petition to get plastic straws out of cafeterias. “This was student-driven,” said Penny Parham, an administrator with the district’s food and nutrition department.