The mission of the Upper School is to provide young women in Groups IX through XII with an academic experience that gives them the knowledge and skills to help them develop wisdom, courage, integrity and compassion. Upper school students learn in a community that strives to embrace shared values while respecting varied opinions as well as a range of teaching and learning styles.

The curriculum encourages students to think critically, logically, creatively and reflectively, to articulate their ideas effectively in a variety of forms and media, to develop habits of physical exercise and good health and to create, appreciate and participate in the arts. In addition to teaching toward understanding in a range of academic disciplines, the Upper School offers students the skills necessary to access and analyze information and to use technology to further their knowledge. The Upper School faculty is committed to helping students develop the understanding and skills to grow and learn both in college and in later life.

Greenwich Academy maintains a coordination program with Brunswick School, a boys' school located five minutes from the GA Campus. The coordinate program of Greenwich Academy and Brunswick School is a partnership of co-equals offering opportunities for greater diversity of students, teachers and programs. Coordination also provides students with a coeducational academic experience while at the same time respecting individual preferences. Through coordination, the two schools are able to offer an enriching experience to students because of the broad range of courses, extracurricular activities and teaching and learning styles made available through this partnership. An underlying principle of coordination is our belief that a school with differences can produce many models for success.

Outside of the classroom, GA girls and Brunswick boys work together on plays, musical performances, some clubs, dances, many social events and some student government projects.