It is unusual to name specific individual educational institutions (universities, schools, etc.) as "vote strongholds" for President Biden.
However, generally speaking, higher education institutions (universities and colleges) across the United States, their faculty, and students are considered one of the strong support bases for the Democratic Party.
Specifically,
the following trends are pointed out:
University Faculty and Staff:
Especially in the liberal arts and social sciences fields,
many faculty members support the Democratic Party,
and political donations tend to gather for Democratic candidates.
Students: Younger voters tend to support the Democratic Party more than older generations, and university campuses are environments with many Democratic supporters.
Education-related Labor Unions:
Major teacher unions
such as the National Education Association
(NEA) and the American Federation of Teachers
(AFT) have historically supported the Democratic Party
and are important sources of funding
and mobilization power in election campaigns.
These unions are a strong support base for President Biden.
Due to these factors, regions where universities are located and areas where many education professionals reside tend to have a higher number of votes for the Democratic Party.