Maria, a US high school student, is busy 1 her studies every day. But after school, she puts down her books and goes off to 2 . She looks after cats at a Humane Society(动物保护协会), helps teachers at school and cleans up the beach. Why? Because about half of US public schools 3 students to do at least 20 hours of community service in order to graduate(毕业). "This project is to give students a 4 of the real world, 5 a habit of volunteering and perhaps explore a career, " said Bob Parks, a teacher at Maria's school. 6 volunteering takes time, Maria enjoys it. " I learn so 7 from it, " she said. She plans to keep volunteering even after she has finished her required hours of work. Maria is now on 8 way towards 250 hours to get a silver medal(银奖)at graduation. She hopes the medal will help her 9 her dream. But some have 10 about the project. Mr. Black, a single(单身的) 11 of four, has to drive his children from one activity to 12 one every weekend. "I have no time to work and rest, " he said. Mike, a volunteering manager, has heard those complaints. He said, "We keep 13 people that volunteer hours are more than for graduation. They are life lessons. " Unlike Mr. Black, some parents agree with the project and want their children to 14 more time volunteering. Michael, a junior, spends Saturdays at JFK Medical Center guiding patients and bringing them newspapers and meals. He is at 258 hours. David, Michael's father, said, "Twenty hours isn't 15 . Children should have more contact(联系) with the world. "