By Kellen Browning, The New York Times Company NEW YORK — Nearly every weekday morning, Valentin Vivar curls up in bed next to his older sister, Araceli, and switches on one of his favorite television shows. The hourlong program, “Let’s Learn NYC!”, isn’t typical children’s fare. Valentin, 5, watches as educators from New York City public schools teach math and science, sing songs and take viewers on virtual field trips to botanical gardens and dance performances.