William Bagley is director of gift planning at St. Mark's School. He is an attorney admitted to state and federal practice in Massachusetts and holds an appointment as an adjunct professor of law at Boston College Law School.

His work in philanthropy extends over thirty years - with postings at leading schools and universities and the nation's oldest land trust. He has advised a Ford Foundation-funded program in affordable housing and a national initiative to eliminate lead poisoning in children as they sought to raise private philanthropic support. In addition, he advises families and family foundations in their philanthropy. His writing on philanthropy owes its origins to a research fellowship at the Yale Divinity School.