I'm not sure exactly how GenMentors are able to count their experience towards GISP certification, but generally there is a process in the GISP application to capture that experience. I believe it is under the heading "GIS Volunteer experience" in the "Contributions to the Profession" area in the Applicants Procedure Manual. However, review the whole document to see if your experience might count in a different area (the requirements change from time to time). Also, be sure to note the documentation requirements so can have the needed information ready for when you do the application.
GISCI Certification Institute (GISP Certification)
Chris Donohue, GISP
Hello and thank you for this information!
I contacted the AAG/Esri ConnectED GeoMentors Program and recieved this additional information:
GeoMentor volunteering can count toward the professional service requirements of the GISP, earning an individual points towards their GISP certification or renewal. Upon reporting a successful GeoMentor engagement, GeoMentors receive a program certificate for their records which is useful for documentation for their GISP certification or renewal. GeoMentors staff may even create a case study from their experience to help encourage others to get involved in the program and the online case study post could be used for documentation as well. To learn more about the GeoMentors program, visit the GeoMentors program website or sign up directly online today.