Things were already slow-moving on Barksdale Boulevard in Bossier City this morning because of construction, but an incident involving a school bus had things at a stand-still.  Bossier City Spokesman Mark Natale says the driver of Bus 25, headed to drop off Bellaire Elementary students at school, tells police two or three male juveniles were walking along the railroad tracks near Sunflower -- when one of them apparently threw a rock at the bus window.  The drives says a dark-haired white male was seen running across the tracks after the rock hit the bus.  Three students on board were injured by flying glass, and one of them was evidently hit with the rock, too...but all of them are doing O.K.  They were treated at the scene.  School officials were onhand to notify parents of the incident. Police are asking anyone with information that can help find whoever committed this malicious act to call them.