Harvard University has banned professors from having "sexual or romantic relationships" with undergraduates, joining Yale and Connecticut universities in enforcing ethical standards of conduct.
Relationships between graduate students and undergraduates are also barred when the graduate student might grade, supervise or evaluate the junior student.
"Undergraduates come to college to learn from us," said Alison Johnson, a Harvard history professor who chaired the panel that wrote the policy. "We're not here to have sexual or romantic relationships with them."
Harvard's earlier policy only prohibited relationships when a student was in the professor's class.
The university-wide review of policy comes in the wake of the US education department's investigations into sexual assault and harassment on many campuses, says Bloomberg.
"It should have been the policy everywhere," said Jack Smith, a senior sociology major who was on the committee that wrote the revision. "Most of the people I've come into contact feel the same way."
Relationships between professors and students are ripe for "exploitation," and faculty members should take steps to ensure "unbiased evaluation" of the student, according to a policy statement of the American Association of University Professors in Washington.
While most faculty members seem to welcome the move, some critics prefer ethical checks without a blanket prohibition which would simply drive it underground.
Arizona State University's faculty voted in favour of toughening a ban on relationships between professors and students in their classes. Yale, in New Haven, Connecticut, banned relationships between undergraduates and faculty in 2010 and the University of Connecticut followed in 2013.
Since then, Yale has disciplined some professors for inappropriate relationships involving both graduate students and undergraduates.