Some Maine fourth-graders are doing their part to help the endangered Atlantic salmon. Pupils at Longfellow Elementary School in Portland raised salmon eggs in class and released the fish into a stream near Highland Lake in Westbrook as part of the ‘‘Fish Friends’’ program. Teachers received a $900 grant from the Portland Education Foundation to pay for an aquarium, a chiller to help keep the water cold enough, and other supplies. The school received 200 salmon eggs in February. Run by the Atlantic Salmon Federation in partnership with the Maine Department of Fisheries, the program teaches students about the endangered Atlantic salmon, a native species.