Sizer's secondary education took place at Phillips Academy in Andover, Massachusetts, which she attended until 1977. Founded in 1778 as a private boarding school, Phillips Academy became coeducational in 1973, and it has since been known for its college-preparatory curriculum.
The Andover setting placed her in the New England independent school tradition before she moved on to Yale University in New Haven, Connecticut, for her undergraduate studies.
Sizer studied at Yale University, where she earned a Bachelor of Arts magna cum laude in 1981. Yale was chartered in 1701 as the Collegiate School in colonial Connecticut, and it grew into one of the oldest and most prominent universities in the United States.
She then attended Harvard Law School, receiving a Juris Doctor cum laude in 1987, the year she was admitted to the Massachusetts bar. Founded in 1817, Harvard Law School is generally regarded as the oldest continuously operating law school in the United States, and its graduates entered a legal profession increasingly shaped by institutional and corporate practice.
Sizer's first professional post was at Yale University, where she served as assistant to the president, A. Bartlett Giamatti, from 1983 to 1984. Giamatti led Yale as president from 1978 until 1986. She returned to the university as assistant to the general counsel from 1987 to 1988, the year she was admitted to the Massachusetts bar.
From 1988 to 1992 she was an associate in the tax and benefits departments of Ropes & Gray, a Boston law firm founded in 1865. Her position there was in the firm's tax and employee benefits practice, which served corporate and institutional clients during a period of growing regulation of retirement and employee benefit plans.
From 1992 to 2000 Sizer worked at Brandeis University as deputy, associate and assistant general counsel. Brandeis, a nonsectarian research university founded in 1948 in Waltham, Massachusetts, named after Louis Brandeis, became the principal institution of her later career. She was senior vice president and general counsel from 2000 to 2013.
From 2014 to 2019 she served as senior counsel, and from 2019 to 2020 she was a partner at Rose Law Partners LLP in Boston. In 2021 she established a solo practice in Cambridge, Massachusetts, focused on the university and college law, serving small private nonprofit colleges. She had been admitted to the First Circuit in 1989 and to the United States Supreme Court in 2000. Her solo practice ran through 2024, and she later described herself as a retired career higher education lawyer.
The Boston Bar Association, founded in 1876 in Boston, is a professional association serving lawyers and the legal community of Massachusetts. Sizer's membership in the association spanned more than three decades, during which she took part in its work on higher education and tax-exempt organizations.
The National Association of College and University Attorneys is a national professional organization for attorneys who advise colleges and universities. Sizer belonged to it from 1992 to 2023, a period that matched her work as in-house and outside counsel for higher education institutions.
Chair of the College and University Law Section (1994–1998); member of the Advisory Committee for the Higher Education Legal Conference, the Steering Committee of the Tax-Exempt Organizations Committee, and the Chapter 180 Task Force.
Boston Bar Association , United States
1987 - 2024
National Association of College and University Attorneys , United States
1992 - 2023
