Many students in Yonkers and the rest of Westchester are heading back to school Tuesday.School and health officials say they are taking extra precautions this year because of swine flu.Officials at many schools in the county say classrooms were fully sanitized before students returned.CDC Director Dr. Thomas Frieden says the spread of swine flu can be reduced by staying home when sick, covering your mouth when coughing or sneezing and washing hands frequently.