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.

“Good afternoon, happy Monday!” Alabsi says to two men, one slumped forward in a wheelchair and wearing soft hospital socks and one slipper. Her voice is cheerful, a soothing contrast to the misery on display in the 50-block neighborhood that’s well-known for its crime, squalor and reckless abandon. “School time. Kids will be coming soon.”