The forces at work in the India of The Revolutionary Optimists, an engaging documentary portrait of several children seeking to improve life in India's slums, appear overwhelming from almost every angle. Co-directors Nicole Newnham and Maren Grainger-Monsen lace their largely observational study with numbers: one clean-water tap for three neighborhoods; 9 million children working in brick mills; 47 percent of girls married by 18.

How does change come to such odds?

One answer emerges from the mission of Bengali community leader Amlan Ganguly: Start small. Ganguly, a former lawyer with a theatrical bent, teaches kids living in urban slums the power of dance, education, and leveraging information for local change. But his key emphasis is on attitude—encouraging those raised with little hope to see in their lives a continuum of possibility.

We follow the subjects over several years, and in two cases Ganguly is no match for India's numbers. A talented dancer marries her abusive boyfriend, and a brickmaker must curtail her education to provide for her family. Hope rides on the thin shoulders of Salim, a fast-talking 11-year-old determined to bring clean water to his community.

Change may be elusive, Optimists confirms, but the will to make it blazes.