It's incredibly valuable real estate: hundreds of acres of public land that sit idle most of the time: New York City school yards. But now Mayor Bloomberg is proposing to turn the vacant yards into beautiful and fully functional public playgrounds. As of today, 69 school playgrounds will be open during after school hours until dusk, and on non-school days, starting at 8:00 a.m., including weekends. Another 290 school playgrounds will be added to the program over the next three years.