Next week (April 15-21) is National Volunteer Week, when organizations across the country will celebrate one of their most important resources: volunteers. In the Boston Public Schools, volunteers play a key role in accelerating student learning. Several organizations -- including Boston Partners in Education, Generations Inc., ReadBoston, and Citizens Schools, to name a few -- recruit, train, and support classroom volunteers. Pictured here is Mary Nickerson (with first grader Victoria Andersen), who has traveled by public bus every Tuesday and Thursday for the past six years to tutor students at the Conley Elementary School in Roslindale. “Ms. Nickerson comes to the Conley whether it is snowing or freezing cold, or the sun is shining,” said Conley principal Kathleen Armstrong.