In December, John R. Green paid a virtual visit to his elementary school alma mater, Old Bonhomme Elementary, to read his children’s books “Dream Jumper” and “Dream Grabber” to more than 80 first-graders. Christine Williams, 70, who retired from full-time teaching in 2005, joined the call as she and Green shared stories and memories with the students; many of them know Williams because she still serves as a volunteer reading specialist at the school.