That’s legal
The New York Human Rights Law prohibits discrimination on the basis of “age, race, creed, color, national origin, sexual orientation, military status, sex, marital status or disability”.
Federal law prevents employment discrimination based on race, color, religion, sex (including pregnancy, sexual orientation, or gender identity), national origin, age (40 or older), disability and genetic information (including family medical history).
What law school you went to is on neither list.
If Harvard’s policies break the rules, that’s not the firm’s issue. However, AFAIK, Harvard is scrupulously fair in their admissions program - so long as you have the grades and the money, they’ll let you in. It’s not Harvard’s fault that most of the people who get the best secondary education and have the most money are predominantly white, Christian, and US born - that’s do to politico-social-historical-economic factors beyond Harvard’s control.