I'm with Lono on this one. Your chances of becoming sick are a function of how many people you come into contact with, not where you come into contact. A healthy kid whose school is closed faces just as great a chance of contracting the virus if he goes to the mall, because he will probably come into contact with just as many people.

Closing schools in NYC may be an overreaction, or it may be out of concern that the available data suggests that the young, healthy populace is being disproportionately infected (as compared to the 'normal' flu that kills 30,000+ each year, mostly elderly and immune sysmtem compromised).