Isabel Gross, an AmeriCorps member with the Aspire! Afterschool Learning - Learning Links program in Arlington, saw the spark of excitement recently working with a student on his science fair project. “(My student) Brian and I were . . . building different kinds of bridges and seeing how many books they would hold before breaking. We were trying to figure out why some bridges held more books than others, and Brian came up with a number of potential factors -- length, different binding materials like glue, tape, and twine -- but could not determine conclusively which one of these had...