The 75 students in Karen Reading’s and Tori Klug’s third-grade classes at North School had two weeks to design and build a container to protect a raw egg during a 25-foot-drop from the roof of the multipurpose building. On Thursday, those containers were tested. The students could use any material to pack their eggs except peanut butter, which Reading said was too messy last year. Parachutes or balloons could slow their descent, or cardboard, plastic or foam could cushion the impact. All eggs were required to be inside sealed plastic bags, though, in case they didn’t survive the fall.