A study tour aims to provide students a quick summary of many highlighted activities and a brief experience of the boarding school life. While summer school will give your child extended opportunities to practice his or her English, and know more about the culture of the country. If you are going to summer school at the school you are applying to, it will help you understand more about the school’s atmosphere, the curriculum and the people there. So I would say summer school is the better choice if you have the time.