As a member of the Association of Mathematics Teachers of New York State, Monahan served as president (2009-2010) and vice president (2006-2007). He served on a number of committees for the New York State Department of Education for writing Regents Exam questions for Math A and Math B, for determining scope and range for the Geometry Regents. He has been a National Trainer for Texas Instruments in Teaching Teachers with Technology since 2001.