On her very first day of student teaching at Linden Avenue Middle School in Red Hook, N.Y., Martha Strever pushed, pulled and pounded on the school’s door, which was locked. No one came. Where was everybody? It was, after all, the first day of school.

It turned out everybody was exactly where they were supposed to be: inside, having entered through the school’s front entrance. Strever had been knocking on a side door. Flustered but undeterred, she not only found her way inside, she also found her life’s calling.

Scarlett Ahmed has started counting the number of people sleeping outside the Queens Career Center in New York City when she arrives at work in the morning.

“It was already bad,” she said. “But this? This will just add to it.”