Wearing a bright safety vest with the words “Safe Passage” on the back, Tatiana Alabsi strides through San Francisco’s Tenderloin neighborhood to its only public elementary school, navigating broken bottles and stained sleeping bags along tired streets that occasionally reek of urine. Along the way in one of America’s most notorious neighborhoods, she calls out to politely alert people huddled on sidewalks, some holding strips of tin foil topped with illicit drugs.