I tend to think of Social Entrepreneurship as more of a mindset, or approach to business than an “area of focus” within business. It tends to attract a different type of personality than the “typical” business/finance major.
You might want to check out Tufts.
It has one of the top undergrad IR programs and a special program in Social Entrepreneurship offered through the Institute for Global Leadership. The most popular minor is in Entrepreneurial Leadership and there are yearly $100K business plan competitions with a Social Entrepreneurship category . It is also one of the top programs for Environmental Economics, as well as for Environmental Engineering/Environmental Health/Environmental Studies. (The current head of the EPA is a Tufts Alum.) It has an entire (separately endowed) College of Citizenship and Public Service.
Undergrad population is 2.5 to 3 times that of Amherst.
Similar difficulty of admissions.