Rescue crews raced frantically through the night to reach students trapped in the rubble of a collapsed school, digging under the glare of floodlights in a disaster where at least 47 people have already died. It is not known how many students were in the school when it collapsed Friday morning. But authorities said roughly 500 children and teenagers typically crowded into the three-story concrete building of College La Promesse, which served classes from kindergarten through high school. The chaotic rescue effort by Red Cross workers, UN peacekeepers and Haitian authorities was inhibited from the start by thousands of grieving neighbors, who blocked the steep, narrow street and fought with school officials to enter the collapsed building in search of their children and friends.