There's also the bulletin board outside of Shaw's in porter- I see quite a few notices of this nature there. There's quite alot of Lesley students wandering through that area.

Perhaps contact the Tufts library, as well? Many universities have tutoring groups already established; the one I attended in Illinois (I worked as an English Composition tutor) allowed people to advertise, as well as took their contact information if they found themselves short on tutors for Math and Sciences.