Fight academic boycotts of Israel.

That’s the message from 101 Jewish and pro-Israel organizations that signed on to a letter sent Tuesday to 250 U.S. college presidents and chancellors whose institutions have previously said they reject such boycotts of the Jewish state. They want the leaders to reaffirm their opposition in light of recent instances in which faculty members objected to study abroad programs in Israel.

Last week, the faculty at Pitzer College in Claremont, California, voted to suspend the school’s study abroad program at Haifa University. This fall, two instructors at the University of Michigan refused to write recommendation letters for students who wished to study in Israel.

“[I]n light of recent reprehensible attempts by faculty at University of Michigan, Pitzer College and elsewhere to implement an academic boycott that thwarts their own students’ academic freedom and their own colleagues’ scholarly activities, it is imperative that university leaders speak out once again, this time even more forcefully,” says the letter organized by the AMCHA initiative, an anti-Semitism campus monitor.

Among the signers are B’nai B’rith International, NCSY, the Simon Wiesenthal Center and the Zionist Organization of America.

Leadership at both universities has criticized the faculty actions. Pitzer’s president called the vote “inconsistent with Pitzer’s core values” while the University of Michigan sanctioned a professor who refused to recommend a student.

Several academic associations, including the American Studies Association in 2013, have voted for boycotts of Israeli universities.