Seems difficult to convince college students to change how they do things, especially since there's a new batch every year (and they have extra-high risk tolerance). Similarly, near the high school you will get lots of high school students biking the wrong way on Trowbridge.

EDIT: But, the city has put up signage in some places directing people to particular streets, so you can ask them for that, might help.

Another alternative is to talk to the city about putting up a contraflow bike lane on Shepard if it's a desire line.

Either way: https://seeclickfix.com or email tpt@cambridgema.gov (Traffic department).