Original sentence: Andrew's-Sewanee School, one of the oldest boarding-day schools in the South, is a private school for grades 7 through 12 with a student population of 100 boarding and 150 day students
Edited sentence: Andrew's-Sewanee School, one of the oldest and best boarding-day schools in the South, is a private school for grades 7 through 12 with a student population of 100 boarding and 150 day students