Melissa Cookhorn, of Brooklyn, said that the two years she spent teaching at a preschool had a profound effect on her. “It reinvigorated me,” she said. “It made me realize I wanted to work with younger students.” Cookhorn has an 11-year-old son and she said that it was difficult to find the time to go back to school on top of her responsibilities as a para-professional in New York City’s Department of Education. “I just decided I would make the time.”