High School is a process to let your child become mature and be ready for college, specially when they attend a boarding school.
In boarding school your child can learn how to take care themselves and how to build relationships with other people. Some boarding schools have many students from different countries, this will only help your high school student gain a broader understanding of the world and different cultures.
Students who live away from home learn a lot about structure, discipline and accountability. These types of students are what colleges and larger corporations are looking for when it comes time to hire new employees.