Answer: Because of the Quakers.
Friends schools are institutions that provide an education based on the beliefs and testimonies of the Religious Society of Friends (Quakers).
Friends schools vary greatly, both in their interpretation of Quaker principles and in how they relate to formal organizations that make up the Society of Friends.
Most Friends schools are similar in their mission: to provide an academically sound education while also instilling values of community, spirituality, responsibility and stewardship in their students
Some institutions founded by Friends were never formally “Quaker Schools.” Some historically Friends institutions are no longer formally associated with the Society of Friends. Those that continue to call themselves “Quaker schools” may have formal oversight from a Friends yearly or monthly meetings, and others are governed by members of the Society of Friends and/or adhere to aspects of Quaker practice.