MONTCLAIR, N.J. — This upscale, racially diverse suburb isn’t the first place you’d expect to see a pitched battle break out over school reform. In recent years, Montclair has become a frequent landing site for middle-class families looking to recreate Manhattan’s Upper West Side on a lawn-bedecked hilltop. It is home to New Jersey’s first medical marijuana dispensary as well as a healthy slice of The New York Times’ editorial staff and is, as one resident puts it, the place you flee to “so you don’t have to fight school wars anymore.”