Final answer:
Hand washing classes for teachers are the primary prevention measure being offered to elementary school teachers to prevent the spread of diseases.
Step-by-step explanation:
The primary prevention measure being offered to elementary school teachers to prevent the spread of diseases is hand washing classes for teachers. Proper hand washing is critical for public health and can help prevent the spread of many pathogens, including those transmitted through direct skin contact or the fecal-oral route. Hand washing classes for teachers can educate them on the correct techniques and importance of hand hygiene.