Sentence:  In high schools with open campuses, students leave at lunchtime to buy <WSD>fast food</WSD> elsewhere. Since leaving school is unsafe, schools are opting to serve less nutritious foods so the students stay on campus. For example, many schools have invited junk food franchises into their cafeterias, including Subway, Taco Bell, and Domino's. 
Meaning of the word marked with <WSD> tags:  A type of food that is quickly made, but of low nutritional value; junk food.